在Ubuntu上为Android系统内置Java应用程序测试Application Frameworks层的硬件服务

在Ubuntu上为Android系统内置Java应用程序测试Application Frameworks层的硬件服务 - 老罗的Android之旅 - 博客频道 - CSDN.NET

?? ? ? ?我们在Android系统增加硬件服务的目的是为了让应用层的APP能够通过Java接口来访问硬件服务。那么， APP如何通过Java接口来访问Application Frameworks层提供的硬件服务呢？在这一篇文章中，我们将在Android系统的应用层增加一个内置的应用程序，这个内置的应用程序通过ServiceManager接口获取指定的服务，然后通过这个服务来获得硬件服务。

?? ? ? ?一. 参照在Ubuntu上为Android系统的Application Frameworks层增加硬件访问服务一文，在Application Frameworks层定义好自己的硬件服务HelloService，并提供IHelloService接口提供访问服务。

?? ? ? 二. 为了方便开发，我们可以在IDE环境下使用Android SDK来开发Android应用程序。开发完成后，再把程序源代码移植到Android源代码工程目录中。使用Eclipse的Android插件ADT创建Android工程很方便，这里不述，可以参考网上其它资料。工程名称为Hello，下面主例出主要文件：

?? ?主程序是src/shy/luo/hello/Hello.java：

?

[java] view plaincopyprint?

1. package?shy.luo.hello;??
2. ??
3. import?shy.luo.hello.R;??
4. import?android.app.Activity;??
5. import?android.os.ServiceManager;??
6. import?android.os.Bundle;??
7. import?android.os.IHelloService;??
8. import?android.os.RemoteException;??
9. import?android.util.Log;??
10. import?android.view.View;??
11. import?android.view.View.OnClickListener;??
12. import?android.widget.Button;??
13. import?android.widget.EditText;??
14. ??
15. public?class?Hello?extends?Activity?implements?OnClickListener?{??
16. ????private?final?static?String?LOG_TAG?=?"shy.luo.renju.Hello";??
17. ??????
18. ????private?IHelloService?helloService?=?null;??
19. ??
20. ????private?EditText?valueText?=?null;??
21. ????private?Button?readButton?=?null;??
22. ????private?Button?writeButton?=?null;??
23. ????private?Button?clearButton?=?null;??
24. ??????
25. ????/**?Called?when?the?activity?is?first?created.?*/??
26. ????@Override??
27. ????public?void?onCreate(Bundle?savedInstanceState)?{??
28. ????????super.onCreate(savedInstanceState);??
29. ????????setContentView(R.layout.main);??
30. ??
31. ????helloService?=?IHelloService.Stub.asInterface(??
32. ????????ServiceManager.getService("hello"));??
33. ??????????
34. ????????valueText?=?(EditText)findViewById(R.id.edit_value);??
35. ????????readButton?=?(Button)findViewById(R.id.button_read);??
36. ????????writeButton?=?(Button)findViewById(R.id.button_write);??
37. ????????clearButton?=?(Button)findViewById(R.id.button_clear);??
38. ??
39. ????readButton.setOnClickListener(this);??
40. ????writeButton.setOnClickListener(this);??
41. ????clearButton.setOnClickListener(this);??
42. ??????????
43. ????????Log.i(LOG_TAG,?"Hello?Activity?Created");??
44. ????}??
45. ??????
46. ????@Override??
47. ????public?void?onClick(View?v)?{??
48. ????????if(v.equals(readButton))?{??
49. ????????try?{??
50. ????????????????int?val?=?helloService.getVal();??
51. ????????????????String?text?=?String.valueOf(val);??
52. ????????????????valueText.setText(text);??
53. ????????}?catch?(RemoteException?e)?{??
54. ????????????Log.e(LOG_TAG,?"Remote?Exception?while?reading?value?from?device.");??
55. ????????}?????????
56. ????????}??
57. ????????else?if(v.equals(writeButton))?{??
58. ????????try?{??
59. ????????????????String?text?=?valueText.getText().toString();??
60. ????????????????int?val?=?Integer.parseInt(text);??
61. ????????????helloService.setVal(val);??
62. ????????}?catch?(RemoteException?e)?{??
63. ????????????Log.e(LOG_TAG,?"Remote?Exception?while?writing?value?to?device.");??
64. ????????}??
65. ????????}??
66. ????????else?if(v.equals(clearButton))?{??
67. ????????????String?text?=?"";??
68. ????????????valueText.setText(text);??
69. ????????}??
70. ????}??
71. }??

package shy.luo.hello;

import shy.luo.hello.R;
import android.app.Activity;
import android.os.ServiceManager;
import android.os.Bundle;
import android.os.IHelloService;
import android.os.RemoteException;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class Hello extends Activity implements OnClickListener {
	private final static String LOG_TAG = "shy.luo.renju.Hello";
	
	private IHelloService helloService = null;

	private EditText valueText = null;
	private Button readButton = null;
	private Button writeButton = null;
	private Button clearButton = null;
	
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

	helloService = IHelloService.Stub.asInterface(
		ServiceManager.getService("hello"));
        
        valueText = (EditText)findViewById(R.id.edit_value);
        readButton = (Button)findViewById(R.id.button_read);
        writeButton = (Button)findViewById(R.id.button_write);
        clearButton = (Button)findViewById(R.id.button_clear);

	readButton.setOnClickListener(this);
	writeButton.setOnClickListener(this);
	clearButton.setOnClickListener(this);
        
        Log.i(LOG_TAG, "Hello Activity Created");
    }
    
    @Override
    public void onClick(View v) {
    	if(v.equals(readButton)) {
		try {
    			int val = helloService.getVal();
    			String text = String.valueOf(val);
    			valueText.setText(text);
		} catch (RemoteException e) {
			Log.e(LOG_TAG, "Remote Exception while reading value from device.");
		}		
    	}
    	else if(v.equals(writeButton)) {
		try {
    			String text = valueText.getText().toString();
    			int val = Integer.parseInt(text);
			helloService.setVal(val);
		} catch (RemoteException e) {
			Log.e(LOG_TAG, "Remote Exception while writing value to device.");
		}
    	}
    	else if(v.equals(clearButton)) {
    		String text = "";
    		valueText.setText(text);
    	}
    }
}

?? ?程序通过ServiceManager.getService("hello")来获得HelloService，接着通过IHelloService.Stub.asInterface函数转换为IHelloService接口。其中，服务名字“hello”是系统启动时加载HelloService时指定的，而IHelloService接口定义在android.os.IHelloService中，具体可以参考在Ubuntu上为Android系统的Application Frameworks层增加硬件访问服务一文。这个程序提供了简单的读定自定义硬件有寄存器val的值的功能，通过IHelloService.getVal和IHelloService.setVal两个接口实现。

?

?

界面布局文件res/layout/main.xml：

[html] view plaincopyprint?

1. <?xml?version="1.0"?encoding="utf-8"?>??
2. ????<LinearLayout?xmlns:android="http://schemas.android.com/apk/res/android"??
3. ???????android:orientation="vertical"??
4. ???????android:layout_width="fill_parent"??
5. ???????android:layout_height="fill_parent">??
6. ???????<LinearLayout??
7. ??????????android:layout_width="fill_parent"??
8. ??????????android:layout_height="wrap_content"??
9. ??????????android:orientation="vertical"???
10. ??????????android:gravity="center">??
11. ??????????<TextView???
12. ?????????????android:layout_width="wrap_content"??
13. ?????????????android:layout_height="wrap_content"???
14. ?????????????android:text="@string/value">??
15. ??????????</TextView>??
16. ??????????<EditText???
17. ?????????????android:layout_width="fill_parent"??
18. ?????????????android:layout_height="wrap_content"???
19. ?????????????android:id="@+id/edit_value"??
20. ?????????????android:hint="@string/hint">??
21. ??????????</EditText>??
22. ???????</LinearLayout>??
23. ???????<LinearLayout??
24. ??????????android:layout_width="fill_parent"??
25. ??????????android:layout_height="wrap_content"??
26. ??????????android:orientation="horizontal"???
27. ??????????android:gravity="center">??
28. ??????????<Button???
29. ?????????????android:id="@+id/button_read"??
30. ?????????????android:layout_width="wrap_content"??
31. ?????????????android:layout_height="wrap_content"??
32. ?????????????android:text="@string/read">??
33. ??????????</Button>??
34. ??????????<Button???
35. ?????????????android:id="@+id/button_write"??
36. ?????????????android:layout_width="wrap_content"??
37. ?????????????android:layout_height="wrap_content"??
38. ?????????????android:text="@string/write">??
39. ??????????</Button>??
40. ??????????<Button???
41. ?????????????android:id="@+id/button_clear"??
42. ?????????????android:layout_width="wrap_content"??
43. ?????????????android:layout_height="wrap_content"??
44. ?????????????android:text="@string/clear">??
45. ??????????</Button>??
46. ???????</LinearLayout>??
47. ????</LinearLayout>??

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
       android:orientation="vertical"
       android:layout_width="fill_parent"
       android:layout_height="fill_parent">
       <LinearLayout
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:orientation="vertical" 
          android:gravity="center">
          <TextView 
             android:layout_width="wrap_content"
             android:layout_height="wrap_content" 
             android:text="@string/value">
          </TextView>
          <EditText 
             android:layout_width="fill_parent"
             android:layout_height="wrap_content" 
             android:id="@+id/edit_value"
             android:hint="@string/hint">
          </EditText>
       </LinearLayout>
       <LinearLayout
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:orientation="horizontal" 
          android:gravity="center">
          <Button 
             android:id="@+id/button_read"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:text="@string/read">
          </Button>
          <Button 
             android:id="@+id/button_write"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:text="@string/write">
          </Button>
          <Button 
             android:id="@+id/button_clear"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:text="@string/clear">
          </Button>
       </LinearLayout>
    </LinearLayout>

字符串文件res/values/strings.xml：

[html] view plaincopyprint?

1. <?xml?version="1.0"?encoding="utf-8"?>??
2. ????<resources>??
3. ???????<string?name="app_name">Hello</string>??
4. ???????<string?name="value">Value</string>??
5. ???????<string?name="hint">Please?input?a?value...</string>??
6. ???????<string?name="read">Read</string>??
7. ???????<string?name="write">Write</string>??
8. ???????<string?name="clear">Clear</string>??
9. ????</resources>??

<?xml version="1.0" encoding="utf-8"?>
    <resources>
       <string name="app_name">Hello</string>
       <string name="value">Value</string>
       <string name="hint">Please input a value...</string>
       <string name="read">Read</string>
       <string name="write">Write</string>
       <string name="clear">Clear</string>
    </resources>

程序描述文件AndroidManifest.xml：

[html] view plaincopyprint?

1. <?xml?version="1.0"?encoding="utf-8"?>??
2. ????<manifest?xmlns:android="http://schemas.android.com/apk/res/android"??
3. ??????package="shy.luo.hello"??
4. ??????android:versionCode="1"??
5. ??????android:versionName="1.0">??
6. ??????<application?android:icon="@drawable/icon"?android:label="@string/app_name">??
7. ????????<activity?android:name=".Hello"??
8. ??????????????????android:label="@string/app_name">??
9. ????????????<intent-filter>??
10. ????????????????<action?android:name="android.intent.action.MAIN"?/>??
11. ????????????????<category?android:name="android.intent.category.LAUNCHER"?/>??
12. ????????????</intent-filter>??
13. ????????</activity>??
14. ??????</application>??
15. ????</manifest>???

<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="shy.luo.hello"
      android:versionCode="1"
      android:versionName="1.0">
      <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Hello"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
      </application>
    </manifest> 

三. 将Hello目录拷贝至packages/experimental目录，新增Android.mk文件：
?? ?USER-NAME@MACHINE-NAME:~/Android/packages/experimental$ vi Android.mk

Android.mk的文件内容如下：

LOCAL_PATH:= $(call my-dir)

include $(CLEAR_VARS)

?

LOCAL_MODULE_TAGS := optional

?

LOCAL_SRC_FILES := $(call all-subdir-java-files)

?

LOCAL_PACKAGE_NAME := Hello

?

include $(BUILD_PACKAGE)

四. 编译：

USER-NAME@MACHINE-NAME:~/Android$ mmm packages/experimental/Hello

编译成功后，便可以在out/target/product/generic/system/app目录下看到Hello.apk文件了。
?? ?五. 重新打包系统镜像文件system.img：

USER-NAME@MACHINE-NAME:~/Android$ make snod
?? ?重新打包后的system.img文件就内置了Hello.apk文件了。

六. 运行Android模拟器：

USER-NAME@MACHINE-NAME:~/Android$ emulator -kernel kernel/common/arch/arm/boot/zImage &

在Home Screen中可以看到Hello应用程序：

?

打开Hello应用程序：

?

点击Read按钮，可以从HelloService中读取硬件寄存器val的值；点击Clear按钮，可以清空文本框的值；在文本框中输入一个数值，再点击Write按钮，便可以将这个值写入到硬件寄存器val中去，可以再次点击Read按钮来验证是否正确写入了值。

至此，我们就完整地学习了在Android的Linux内核空间添加硬件驱动程序、在Android的硬件抽象层添加硬件接口、在Android的Application Frameworks层提供硬件服务以及在Android的应用层调用硬件服务的整个过程了，希望能为读者进入Android系统提供入门帮助。重新学习整个过程，请参考Android硬件抽象层（HAL）概要介绍和学习计划。

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