Android技术精髓-理解Context [源码]
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Launch multiple new activities.
|
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Same as
startActivities(Intent[],
Bundle) with no options specified. |
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Same as
startActivity(Intent,
Bundle) with no options specified. |
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Launch a new activity.
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public abstract void startActivity(Intent intent);
public abstract boolean stopService(Intent service);
public abstract boolean bindService(Intent service, ServiceConnection conn,
int flags);
public abstract void unbindService(ServiceConnection conn);
Context相关类的继承关系
/**
* Common implementation of Context API, which provides the base
* context object for Activity and other application components.
*/
class ContextImpl extends Context {
private final static String TAG = "ApplicationContext";
private final static boolean DEBUG = false;
private final static boolean DEBUG_ICONS = false;
//以下选择部分function实现源码贴出
@Override
public PackageManager getPackageManager() {
if (mPackageManager != null) {
return mPackageManager;
}
IPackageManager pm = ActivityThread.getPackageManager();
if (pm != null) {
// Doesn‘t matter if we make more than one instance.
return (mPackageManager = new ApplicationPackageManager(this, pm));
}
return null;
}
@Override
public void setTheme(int resid) {
mThemeResource = resid;
}
@Override
public Resources.Theme getTheme() {
if (mTheme == null) {
if (mThemeResource == 0) {
mThemeResource = com.android.internal.R.style.Theme;
}
mTheme = mResources.newTheme();
mTheme.applyStyle(mThemeResource, true);
}
return mTheme;
}
private static File makeBackupFile(File prefsFile) {
return new File(prefsFile.getPath() + ".bak");
}
public File getSharedPrefsFile(String name) {
return makeFilename(getPreferencesDir(), name + ".xml");
}
@Override
public SharedPreferences getSharedPreferences(String name, int mode) {
SharedPreferencesImpl sp;
File prefsFile;
boolean needInitialLoad = false;
synchronized (sSharedPrefs) {
sp = sSharedPrefs.get(name);
if (sp != null && !sp.hasFileChangedUnexpectedly()) {
return sp;
}
prefsFile = getSharedPrefsFile(name);
if (sp == null) {
sp = new SharedPreferencesImpl(prefsFile, mode, null);
sSharedPrefs.put(name, sp);
needInitialLoad = true;
}
}
synchronized (sp) {
if (needInitialLoad && sp.isLoaded()) {
// lost the race to load; another thread handled it
return sp;
}
File backup = makeBackupFile(prefsFile);
if (backup.exists()) {
prefsFile.delete();
backup.renameTo(prefsFile);
}
// Debugging
if (prefsFile.exists() && !prefsFile.canRead()) {
Log.w(TAG, "Attempt to read preferences file " + prefsFile + " without permission");
}
Map map = null;
FileStatus stat = new FileStatus();
if (FileUtils.getFileStatus(prefsFile.getPath(), stat) && prefsFile.canRead()) {
try {
FileInputStream str = new FileInputStream(prefsFile);
map = XmlUtils.readMapXml(str);
str.close();
} catch (org.xmlpull.v1.XmlPullParserException e) {
Log.w(TAG, "getSharedPreferences", e);
} catch (FileNotFoundException e) {
Log.w(TAG, "getSharedPreferences", e);
} catch (IOException e) {
Log.w(TAG, "getSharedPreferences", e);
}
}
sp.replace(map, stat);
}
return sp;
}
private File getPreferencesDir() {
synchronized (mSync) {
if (mPreferencesDir == null) {
mPreferencesDir = new File(getDataDirFile(), "shared_prefs");
}
return mPreferencesDir;
}
}
@Override
public FileInputStream openFileInput(String name)
throws FileNotFoundException {
File f = makeFilename(getFilesDir(), name);
return new FileInputStream(f);
}
@Override
public FileOutputStream openFileOutput(String name, int mode)
throws FileNotFoundException {
final boolean append = (mode&MODE_APPEND) != 0;
File f = makeFilename(getFilesDir(), name);
try {
FileOutputStream fos = new FileOutputStream(f, append);
setFilePermissionsFromMode(f.getPath(), mode, 0);
return fos;
} catch (FileNotFoundException e) {
}
File parent = f.getParentFile();
parent.mkdir();
FileUtils.setPermissions(
parent.getPath(),
FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,
-1, -1);
FileOutputStream fos = new FileOutputStream(f, append);
setFilePermissionsFromMode(f.getPath(), mode, 0);
return fos;
}
@Override
public boolean deleteFile(String name) {
File f = makeFilename(getFilesDir(), name);
return f.delete();
}
@Override
public File getFilesDir() {
synchronized (mSync) {
if (mFilesDir == null) {
mFilesDir = new File(getDataDirFile(), "files");
}
if (!mFilesDir.exists()) {
if(!mFilesDir.mkdirs()) {
Log.w(TAG, "Unable to create files directory");
return null;
}
FileUtils.setPermissions(
mFilesDir.getPath(),
FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,
-1, -1);
}
return mFilesDir;
}
}
@Override
public void startActivity(Intent intent) {
if ((intent.getFlags()&Intent.FLAG_ACTIVITY_NEW_TASK) == 0) {
throw new AndroidRuntimeException(
"Calling startActivity() from outside of an Activity "
+ " context requires the FLAG_ACTIVITY_NEW_TASK flag."
+ " Is this really what you want?");
}
mMainThread.getInstrumentation().execStartActivity(
getOuterContext(), mMainThread.getApplicationThread(), null, null, intent, -1);
}
@Override
public void sendBroadcast(Intent intent, String receiverPermission) {
String resolvedType = intent.resolveTypeIfNeeded(getContentResolver());
try {
ActivityManagerNative.getDefault().broadcastIntent(
mMainThread.getApplicationThread(), intent, resolvedType, null,
Activity.RESULT_OK, null, null, receiverPermission, false, false);
} catch (RemoteException e) {
}
}
@Override
public ComponentName startService(Intent service) {
try {
ComponentName cn = ActivityManagerNative.getDefault().startService(
mMainThread.getApplicationThread(), service,
service.resolveTypeIfNeeded(getContentResolver()));
if (cn != null && cn.getPackageName().equals("!")) {
throw new SecurityException(
"Not allowed to start service " + service
+ " without permission " + cn.getClassName());
}
return cn;
} catch (RemoteException e) {
return null;
}
}
@Override
public boolean stopService(Intent service) {
try {
int res = ActivityManagerNative.getDefault().stopService(
mMainThread.getApplicationThread(), service,
service.resolveTypeIfNeeded(getContentResolver()));
if (res < 0) {
throw new SecurityException(
"Not allowed to stop service " + service);
}
return res != 0;
} catch (RemoteException e) {
return false;
}
}
@Override
public boolean bindService(Intent service, ServiceConnection conn,
int flags) {
IServiceConnection sd;
if (mPackageInfo != null) {
sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(),
mMainThread.getHandler(), flags);
} else {
throw new RuntimeException("Not supported in system context");
}
try {
int res = ActivityManagerNative.getDefault().bindService(
mMainThread.getApplicationThread(), getActivityToken(),
service, service.resolveTypeIfNeeded(getContentResolver()),
sd, flags);
if (res < 0) {
throw new SecurityException(
"Not allowed to bind to service " + service);
}
return res != 0;
} catch (RemoteException e) {
return false;
}
}
@Override
public void unbindService(ServiceConnection conn) {
if (mPackageInfo != null) {
IServiceConnection sd = mPackageInfo.forgetServiceDispatcher(
getOuterContext(), conn);
try {
ActivityManagerNative.getDefault().unbindService(sd);
} catch (RemoteException e) {
}
} else {
throw new RuntimeException("Not supported in system context");
}
}
@Override
public Object getSystemService(String name) {
if (WINDOW_SERVICE.equals(name)) {
return WindowManagerImpl.getDefault();
} else if (LAYOUT_INFLATER_SERVICE.equals(name)) {
synchronized (mSync) {
LayoutInflater inflater = mLayoutInflater;
if (inflater != null) {
return inflater;
}
mLayoutInflater = inflater =
PolicyManager.makeNewLayoutInflater(getOuterContext());
return inflater;
}
} else if (ACTIVITY_SERVICE.equals(name)) {
return getActivityManager();
} else if (INPUT_METHOD_SERVICE.equals(name)) {
return InputMethodManager.getInstance(this);
} else if (ALARM_SERVICE.equals(name)) {
return getAlarmManager();
} else if (ACCOUNT_SERVICE.equals(name)) {
return getAccountManager();
} else if (POWER_SERVICE.equals(name)) {
return getPowerManager();
} else if (CONNECTIVITY_SERVICE.equals(name)) {
return getConnectivityManager();
} else if (THROTTLE_SERVICE.equals(name)) {
return getThrottleManager();
} else if (WIFI_SERVICE.equals(name)) {
return getWifiManager();
} else if (NOTIFICATION_SERVICE.equals(name)) {
return getNotificationManager();
} else if (KEYGUARD_SERVICE.equals(name)) {
return new KeyguardManager();
} else if (ACCESSIBILITY_SERVICE.equals(name)) {
return AccessibilityManager.getInstance(this);
} else if (LOCATION_SERVICE.equals(name)) {
return getLocationManager();
} else if (SEARCH_SERVICE.equals(name)) {
return getSearchManager();
} else if (SENSOR_SERVICE.equals(name)) {
return getSensorManager();
} else if (STORAGE_SERVICE.equals(name)) {
return getStorageManager();
} else if (VIBRATOR_SERVICE.equals(name)) {
return getVibrator();
} else if (STATUS_BAR_SERVICE.equals(name)) {
synchronized (mSync) {
if (mStatusBarManager == null) {
mStatusBarManager = new StatusBarManager(getOuterContext());
}
return mStatusBarManager;
}
} else if (AUDIO_SERVICE.equals(name)) {
return getAudioManager();
} else if (TELEPHONY_SERVICE.equals(name)) {
return getTelephonyManager();
} else if (CLIPBOARD_SERVICE.equals(name)) {
return getClipboardManager();
} else if (WALLPAPER_SERVICE.equals(name)) {
return getWallpaperManager();
} else if (DROPBOX_SERVICE.equals(name)) {
return getDropBoxManager();
} else if (DEVICE_POLICY_SERVICE.equals(name)) {
return getDevicePolicyManager();
} else if (UI_MODE_SERVICE.equals(name)) {
return getUiModeManager();
} else if (DOWNLOAD_SERVICE.equals(name)) {
return getDownloadManager();
} else if (NFC_SERVICE.equals(name)) {
return getNfcManager();
}
return null;
}
该类只是对Context类的一种包装,该类的构造函数包含了一个真正的Context引用,即ContextIml对象
源码:
public class ContextWrapper extends Context {
Context mBase;
public ContextWrapper(Context base) {
mBase = base;
}
/**
* Set the base context for this ContextWrapper. All calls will then be
* delegated to the base context. Throws
* IllegalStateException if a base context has already been set.
*
* @param base The new base context for this wrapper.
*/
protected void attachBaseContext(Context base) {
if (mBase != null) {
throw new IllegalStateException("Base context already set");
}
mBase = base;
}
/**
* @return the base context as set by the constructor or setBaseContext
*/
public Context getBaseContext() {
return mBase;
}
@Override
public AssetManager getAssets() {
return mBase.getAssets();
}
@Override
public Resources getResources()
{
return mBase.getResources();
}
@Override
public PackageManager getPackageManager() {
return mBase.getPackageManager();
}
@Override
public ContentResolver getContentResolver() {
return mBase.getContentResolver();
}
@Override
public Looper getMainLooper() {
return mBase.getMainLooper();
}
@Override
public Context getApplicationContext() {
return mBase.getApplicationContext();
}
@Override
public void setTheme(int resid) {
mBase.setTheme(resid);
}
@Override
public Resources.Theme getTheme() {
return mBase.getTheme();
}
@Override
public ClassLoader getClassLoader() {
return mBase.getClassLoader();
}
@Override
public String getPackageName() {
return mBase.getPackageName();
}
@Override
public ApplicationInfo getApplicationInfo() {
return mBase.getApplicationInfo();
}
@Override
public String getPackageResourcePath() {
return mBase.getPackageResourcePath();
}
@Override
public String getPackageCodePath() {
return mBase.getPackageCodePath();
}
/** @hide */
@Override
public File getSharedPrefsFile(String name) {
return mBase.getSharedPrefsFile(name);
}
@Override
public SharedPreferences getSharedPreferences(String name, int mode) {
return mBase.getSharedPreferences(name, mode);
}
@Override
public FileInputStream openFileInput(String name)
throws FileNotFoundException {
return mBase.openFileInput(name);
}
@Override
public FileOutputStream openFileOutput(String name, int mode)
throws FileNotFoundException {
return mBase.openFileOutput(name, mode);
}
@Override
public boolean deleteFile(String name) {
return mBase.deleteFile(name);
ContextThemeWrapper类 :
该类内部包含了主题(Theme)相关的接口,即android:theme属性指定的。只有Activity需要主题,Service不需要主题, 所以Service直接继承于ContextWrapper类。
源码:
/**
* A ContextWrapper that allows you to modify the theme from what is in the
* wrapped context.
*/
public class ContextThemeWrapper extends ContextWrapper {
private Context mBase;
private int mThemeResource;
private Resources.Theme mTheme;
private LayoutInflater mInflater;
public ContextThemeWrapper() {
super(null);
}
public ContextThemeWrapper(Context base, int themeres) {
super(base);
mBase = base;
mThemeResource = themeres;
}
@Override protected void attachBaseContext(Context newBase) {
super.attachBaseContext(newBase);
mBase = newBase;
}
@Override public void setTheme(int resid) {
mThemeResource = resid;
initializeTheme();
}
@Override public Resources.Theme getTheme() {
if (mTheme != null) {
return mTheme;
}
if (mThemeResource == 0) {
mThemeResource = com.android.internal.R.style.Theme;
}
initializeTheme();
return mTheme;
}
@Override public Object getSystemService(String name) {
if (LAYOUT_INFLATER_SERVICE.equals(name)) {
if (mInflater == null) {
mInflater = LayoutInflater.from(mBase).cloneInContext(this);
}
return mInflater;
}
return mBase.getSystemService(name);
}
/**
* Called by {@link #setTheme} and {@link #getTheme} to apply a theme
* resource to the current Theme object. Can override to change the
* default (simple) behavior. This method will not be called in multiple
* threads simultaneously.
*
* @param theme The Theme object being modified.
* @param resid The theme style resource being applied to <var>theme</var>.
* @param first Set to true if this is the first time a style is being
* applied to <var>theme</var>.
*/
protected void onApplyThemeResource(Resources.Theme theme, int resid, boolean first) {
theme.applyStyle(resid, true);
}
private void initializeTheme() {
final boolean first = mTheme == null;
if (first) {
mTheme = getResources().newTheme();
Resources.Theme theme = mBase.getTheme();
if (theme != null) {
mTheme.setTo(theme);
}
}
onApplyThemeResource(mTheme, mThemeResource, first);
}
}
Activity类源码(部分):
public class Activity extends ContextThemeWrapper
implements LayoutInflater.Factory,
Window.Callback, KeyEvent.Callback,
OnCreateContextMenuListener, ComponentCallbacks {
private static final String TAG = "Activity";
public static long getInstanceCount() {
return sInstanceCount;
}
/** Return the intent that started this activity. */
public Intent getIntent() {
return mIntent;
}
/**
* Change the intent returned by {@link #getIntent}. This holds a
* reference to the given intent; it does not copy it. Often used in
* conjunction with {@link #onNewIntent}.
*
* @param newIntent The new Intent object to return from getIntent
*
* @see #getIntent
* @see #onNewIntent
*/
public void setIntent(Intent newIntent) {
mIntent = newIntent;
}
/** Return the application that owns this activity. */
public final Application getApplication() {
return mApplication;
}
/** Is this activity embedded inside of another activity? */
public final boolean isChild() {
return mParent != null;
}
/** Return the parent activity if this view is an embedded child. */
public final Activity getParent() {
return mParent;
}
/** Retrieve the window manager for showing custom windows. */
public WindowManager getWindowManager() {
return mWindowManager;
}
/**
* Called when the activity is starting. This is where most initialization
* should go: calling {@link #setContentView(int)} to inflate the
* activity‘s UI, using {@link #findViewById} to programmatically interact
* with widgets in the UI, calling
* {@link #managedQuery(android.net.Uri , String[], String, String[], String)} to retrieve
* cursors for data being displayed, etc.
*
* <p>You can call {@link #finish} from within this function, in
* which case onDestroy() will be immediately called without any of the rest
* of the activity lifecycle ({@link #onStart}, {@link #onResume},
* {@link #onPause}, etc) executing.
*
* <p><em>Derived classes must call through to the super class‘s
* implementation of this method. If they do not, an exception will be
* thrown.</em></p>
*
* @param savedInstanceState If the activity is being re-initialized after
* previously being shut down then this Bundle contains the data it most
* recently supplied in {@link #onSaveInstanceState}. <b><i>Note: Otherwise it is null.</i></b>
*
* @see #onStart
* @see #onSaveInstanceState
* @see #onRestoreInstanceState
* @see #onPostCreate
*/
protected void onCreate(Bundle savedInstanceState) {
mVisibleFromClient = !mWindow.getWindowStyle().getBoolean(
com.android.internal.R.styleable.Window_windowNoDisplay, false);
mCalled = true;
}
private Dialog createDialog(Integer dialogId, Bundle state, Bundle args) {
final Dialog dialog = onCreateDialog(dialogId, args);
if (dialog == null) {
return null;
}
dialog.dispatchOnCreate(state);
return dialog;
}
protected void onDestroy() {
mCalled = true;
// dismiss any dialogs we are managing.
if (mManagedDialogs != null) {
final int numDialogs = mManagedDialogs.size();
for (int i = 0; i < numDialogs; i++) {
final ManagedDialog md = mManagedDialogs.valueAt(i);
if (md.mDialog.isShowing()) {
md.mDialog.dismiss();
}
}
mManagedDialogs = null;
}
// close any cursors we are managing.
synchronized (mManagedCursors) {
int numCursors = mManagedCursors.size();
for (int i = 0; i < numCursors; i++) {
ManagedCursor c = mManagedCursors.get(i);
if (c != null) {
c.mCursor.close();
}
}
mManagedCursors.clear();
}
// Close any open search dialog
if (mSearchManager != null) {
mSearchManager.stopSearch();
}
}
/**
* Called when a key was pressed down and not handled by any of the views
* inside of the activity. So, for example, key presses while the cursor
* is inside a TextView will not trigger the event (unless it is a navigation
* to another object) because TextView handles its own key presses.
*
* <p>If the focused view didn‘t want this event, this method is called.
*
* <p>The default implementation takes care of {@link KeyEvent#KEYCODE_BACK}
* by calling {@link #onBackPressed()}, though the behavior varies based
* on the application compatibility mode: for
* {@link android.os.Build.VERSION_CODES#ECLAIR} or later applications,
* it will set up the dispatch to call {@link #onKeyUp} where the action
* will be performed; for earlier applications, it will perform the
* action immediately in on-down, as those versions of the platform
* behaved.
*
* <p>Other additional default key handling may be performed
* if configured with {@link #setDefaultKeyMode}.
*
* @return Return <code>true</code> to prevent this event from being propagated
* further, or <code>false</code> to indicate that you have not handled
* this event and it should continue to be propagated.
* @see #onKeyUp
* @see android.view.KeyEvent
*/
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
if (getApplicationInfo().targetSdkVersion
>= Build.VERSION_CODES.ECLAIR) {
event.startTracking();
} else {
onBackPressed();
}
return true;
}
if (mDefaultKeyMode == DEFAULT_KEYS_DISABLE) {
return false;
} else if (mDefaultKeyMode == DEFAULT_KEYS_SHORTCUT) {
if (getWindow().performPanelShortcut(Window.FEATURE_OPTIONS_PANEL,
keyCode, event, Menu.FLAG_ALWAYS_PERFORM_CLOSE)) {
return true;
}
return false;
} else {
// Common code for DEFAULT_KEYS_DIALER & DEFAULT_KEYS_SEARCH_*
boolean clearSpannable = false;
boolean handled;
if ((event.getRepeatCount() != 0) || event.isSystem()) {
clearSpannable = true;
handled = false;
} else {
handled = TextKeyListener.getInstance().onKeyDown(
null, mDefaultKeySsb, keyCode, event);
if (handled && mDefaultKeySsb.length() > 0) {
// something useable has been typed - dispatch it now.
final String str = mDefaultKeySsb.toString();
clearSpannable = true;
switch (mDefaultKeyMode) {
case DEFAULT_KEYS_DIALER:
Intent intent = new Intent(Intent.ACTION_DIAL, Uri.parse("tel:" + str));
intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);
break;
case DEFAULT_KEYS_SEARCH_LOCAL:
startSearch(str, false, null, false);
break;
case DEFAULT_KEYS_SEARCH_GLOBAL:
startSearch(str, false, null, true);
break;
}
}
}
if (clearSpannable) {
mDefaultKeySsb.clear();
mDefaultKeySsb.clearSpans();
Selection.setSelection(mDefaultKeySsb,0);
}
return handled;
}
}
/**
* Default implementation of {@link KeyEvent.Callback#onKeyLongPress(int, KeyEvent)
* KeyEvent.Callback.onKeyLongPress()}: always returns false (doesn‘t handle
* the event).
*/
public boolean onKeyLongPress(int keyCode, KeyEvent event) {
return false;
}
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (getApplicationInfo().targetSdkVersion
>= Build.VERSION_CODES.ECLAIR) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.isTracking()
&& !event.isCanceled()) {
onBackPressed();
return true;
}
}
return false;
}
/**
* Default implementation of {@link KeyEvent.Callback#onKeyMultiple(int, int, KeyEvent)
* KeyEvent.Callback.onKeyMultiple()}: always returns false (doesn‘t handle
* the event).
*/
public boolean onKeyMultiple(int keyCode, int repeatCount, KeyEvent event) {
return false;
}
/**
* Called when the activity has detected the user‘s press of the back
* key. The default implementation simply finishes the current activity,
* but you can override this to do whatever you want.
*/
public void onBackPressed() {
finish();
}
@Override
public void startActivity(Intent intent) {
startActivityForResult(intent, -1);
}
public void startActivityFromChild(Activity child, Intent intent,
int requestCode) {
Instrumentation.ActivityResult ar =
mInstrumentation.execStartActivity(
this, mMainThread.getApplicationThread(), mToken, child,
intent, requestCode);
if (ar != null) {
mMainThread.sendActivityResult(
mToken, child.mEmbeddedID, requestCode,
ar.getResultCode(), ar.getResultData());
}
}
public void finish() {
if (mParent == null) {
int resultCode;
Intent resultData;
synchronized (this) {
resultCode = mResultCode;
resultData = mResultData;
}
if (Config.LOGV) Log.v(TAG, "Finishing self: token=" + mToken);
try {
if (ActivityManagerNative.getDefault()
.finishActivity(mToken, resultCode, resultData)) {
mFinished = true;
}
} catch (RemoteException e) {
// Empty
}
} else {
mParent.finishFromChild(this);
}
}
public void finishFromChild(Activity child) {
finish();
}
/**
* Force finish another activity that you had previously started with
* {@link #startActivityForResult}.
*
* @param requestCode The request code of the activity that you had
* given to startActivityForResult(). If there are multiple
* activities started with this request code, they
* will all be finished.
*/
public void finishActivity(int requestCode) {
if (mParent == null) {
try {
ActivityManagerNative.getDefault()
.finishSubActivity(mToken, mEmbeddedID, requestCode);
} catch (RemoteException e) {
// Empty
}
} else {
mParent.finishActivityFromChild(this, requestCode);
}
} {
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