Android PopupWindow的使用和分析

 

Android PopupWindow的使用和分析

 

PopupWindow使用

       PopupWindow这个类用来实现一个弹出框,可以使用任意布局的View作为其内容,这个弹出框是悬浮在当前activity之上的。

 

PopupWindow使用Demo

  这个类的使用,不再过多解释,直接上代码吧。

  比如弹出框的布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="#FFBBFFBB"
    android:orientation="vertical" >

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="10dp"
        android:text="Hello My Window"
        android:textSize="20sp" />

    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="10dp"
        android:text="Button"
        android:textSize="20sp" />

</LinearLayout>
弹出框布局

 

  Activity的布局中只有一个按钮,按下后会弹出框,Activity代码如下:

package com.example.hellopopupwindow;

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.PopupWindow;
import android.widget.Toast;

public class MainActivity extends Activity {

    private Context mContext = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mContext = this;

        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {

                showPopupWindow(view);
            }
        });
    }

    private void showPopupWindow(View view) {

        // 一个自定义的布局,作为显示的内容
        View contentView = LayoutInflater.from(mContext).inflate(
                R.layout.pop_window, null);
        // 设置按钮的点击事件
        Button button = (Button) contentView.findViewById(R.id.button1);
        button.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                Toast.makeText(mContext, "button is pressed",
                        Toast.LENGTH_SHORT).show();
            }
        });

        final PopupWindow popupWindow = new PopupWindow(contentView,
                LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, true);

        popupWindow.setTouchable(true);

        popupWindow.setTouchInterceptor(new OnTouchListener() {

            @Override
            public boolean onTouch(View v, MotionEvent event) {

                Log.i("mengdd", "onTouch : ");

                return false;
                // 这里如果返回true的话,touch事件将被拦截
                // 拦截后 PopupWindow的onTouchEvent不被调用,这样点击外部区域无法dismiss
            }
        });

        // 如果不设置PopupWindow的背景,无论是点击外部区域还是Back键都无法dismiss弹框
        // 我觉得这里是API的一个bug
        popupWindow.setBackgroundDrawable(getResources().getDrawable(
                R.drawable.selectmenu_bg_downward));

        // 设置好参数之后再show
        popupWindow.showAsDropDown(view);

    }

}

 

 

  弹出框的布局中有一个TextView和一个Button,Button点击后显示Toast,如图:

 

 

  第一次实现的时候遇到了问题,就是弹出框不会在按下Back键的时候消失,点击弹框外区域也没有正常消失,搜索了一下,都说只要设置背景就好了。

  然后我就找了个图片,果然弹框能正常dismiss了(见注释)。

 

PopupWindow源码分析

  为了解答一下上面的问题,看看源码(最新API Level 19,Android 4.4.2)。

1.显示方法

  显示提供了两种形式:

  showAtLocation()显示在指定位置,有两个方法重载:

public void showAtLocation(View parent, int gravity, int x, int y)

public void showAtLocation(IBinder token, int gravity, int x, int y)

 

  showAsDropDown()显示在一个参照物View的周围,有三个方法重载:

public void showAsDropDown(View anchor)

public void showAsDropDown(View anchor, int xoff, int yoff)

public void showAsDropDown(View anchor, int xoff, int yoff, int gravity)

  最后一种带Gravity参数的方法是API 19新引入的。

 

  弹出的方法中首先需要preparePopup(),最后再invokePopup()

  prepare的方法中可以看到有无背景的分别:

   /**
     * <p>Prepare the popup by embedding in into a new ViewGroup if the
     * background drawable is not null. If embedding is required, the layout
     * parameters‘ height is mnodified to take into account the background‘s
     * padding.</p>
     *
     * @param p the layout parameters of the popup‘s content view
     */
    private void preparePopup(WindowManager.LayoutParams p) {
        if (mContentView == null || mContext == null || mWindowManager == null) {
            throw new IllegalStateException("You must specify a valid content view by "
                    + "calling setContentView() before attempting to show the popup.");
        }

        if (mBackground != null) {
            final ViewGroup.LayoutParams layoutParams = mContentView.getLayoutParams();
            int height = ViewGroup.LayoutParams.MATCH_PARENT;
            if (layoutParams != null &&
                    layoutParams.height == ViewGroup.LayoutParams.WRAP_CONTENT) {
                height = ViewGroup.LayoutParams.WRAP_CONTENT;
            }

            // when a background is available, we embed the content view
            // within another view that owns the background drawable
            PopupViewContainer popupViewContainer = new PopupViewContainer(mContext);
            PopupViewContainer.LayoutParams listParams = new PopupViewContainer.LayoutParams(
                    ViewGroup.LayoutParams.MATCH_PARENT, height
            );
            popupViewContainer.setBackgroundDrawable(mBackground);
            popupViewContainer.addView(mContentView, listParams);

            mPopupView = popupViewContainer;
        } else {
            mPopupView = mContentView;
        }
        mPopupViewInitialLayoutDirectionInherited =
                (mPopupView.getRawLayoutDirection() == View.LAYOUT_DIRECTION_INHERIT);
        mPopupWidth = p.width;
        mPopupHeight = p.height;
    }

 

 

2.背景是否为空对Touch事件的影响

  如果有背景,则会在contentView外面包一层PopupViewContainer之后作为mPopupView,如果没有背景,则直接用contentView作为mPopupView。

  而这个PopupViewContainer是一个内部私有类,它继承了FrameLayout,在其中重写了Key和Touch事件的分发处理:

 @Override
        public boolean dispatchKeyEvent(KeyEvent event) {
            if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {
                if (getKeyDispatcherState() == null) {
                    return super.dispatchKeyEvent(event);
                }

                if (event.getAction() == KeyEvent.ACTION_DOWN
                        && event.getRepeatCount() == 0) {
                    KeyEvent.DispatcherState state = getKeyDispatcherState();
                    if (state != null) {
                        state.startTracking(event, this);
                    }
                    return true;
                } else if (event.getAction() == KeyEvent.ACTION_UP) {
                    KeyEvent.DispatcherState state = getKeyDispatcherState();
                    if (state != null && state.isTracking(event) && !event.isCanceled()) {
                        dismiss();
                        return true;
                    }
                }
                return super.dispatchKeyEvent(event);
            } else {
                return super.dispatchKeyEvent(event);
            }
        }

        @Override
        public boolean dispatchTouchEvent(MotionEvent ev) {
            if (mTouchInterceptor != null && mTouchInterceptor.onTouch(this, ev)) {
                return true;
            }
            return super.dispatchTouchEvent(ev);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event) {
            final int x = (int) event.getX();
            final int y = (int) event.getY();
            
            if ((event.getAction() == MotionEvent.ACTION_DOWN)
                    && ((x < 0) || (x >= getWidth()) || (y < 0) || (y >= getHeight()))) {
                dismiss();
                return true;
            } else if (event.getAction() == MotionEvent.ACTION_OUTSIDE) {
                dismiss();
                return true;
            } else {
                return super.onTouchEvent(event);
            }
        }

  由于PopupView本身并没有重写Key和Touch事件的处理,所以如果没有包这个外层容器类,点击Back键或者外部区域是不会导致弹框消失的。

 

 

Reference

  http://developer.android.com/reference/android/widget/PopupWindow.html

 

Android PopupWindow的使用和分析,,5-wow.com

郑重声明:本站内容如果来自互联网及其他传播媒体,其版权均属原媒体及文章作者所有。转载目的在于传递更多信息及用于网络分享,并不代表本站赞同其观点和对其真实性负责,也不构成任何其他建议。