Float Window

出处：http://www.jb51.net/article/32321.htm

用过新版本android 360手机助手都人都对 360中只在桌面显示一个小小悬浮窗口羡慕不已吧？ 
其实实现这种功能，主要有两步： 
1.判断当前显示的是为桌面。这个内容我在前面的帖子里面已经有过介绍，如果还没看过的赶快稳步看一下哦。 
2.使用windowManager往最顶层添加一个View 
.这个知识点就是为本文主要讲解的内容哦。在本文的讲解中，我们还会讲到下面的知识点： 
a.如果获取到状态栏的高度 
b.悬浮窗口的拖动 
c.悬浮窗口的点击事件 

FloatView 代码：

import android.content.Context;
import android.graphics.Rect;
import android.util.Log;
import android.view.MotionEvent;
import android.view.WindowManager;
import android.widget.ImageView;

public class FloatView extends ImageView {
	private final static String TAG = "FloatView";
	private float mTouchX;
	private float mTouchY;
	private float x;
	private float y;
	private float mStartX;
	private float mStartY;
	private OnClickListener mClickListener;
	private WindowManager windowManager = (WindowManager) getContext().getApplicationContext().getSystemService(Context.WINDOW_SERVICE);
	// this windowManagerParams is system variable, to save window params.
	private WindowManager.LayoutParams windowManagerParams = ((FloatApplication) getContext().getApplicationContext()).getWindowParams();

	public FloatView(Context context) {
		super(context);
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		// Get the status bar height.
		Rect frame = new Rect();
		getWindowVisibleDisplayFrame(frame);
		int statusBarHeight = frame.top;
		Log.e(TAG,"statusBarHeight:" + statusBarHeight);
		// get the x and y, base on left-top point.
		x = event.getRawX();
		y = event.getRawY() - statusBarHeight; // statusBarHeight is the height of system status bar.
		Log.e(TAG, "currX" + x + "====currY" + y);
		switch (event.getAction()) {
		case MotionEvent.ACTION_DOWN: // get the motion of finger
			// get the view x&y, base on left-top point
			mTouchX = event.getX();
			mTouchY = event.getY();
			mStartX = x;
			mStartY = y;
			Log.e(TAG, "startX" + mTouchX + "====startY" + mTouchY);
			break;
		case MotionEvent.ACTION_MOVE: // get the motion of finger.
			updateViewPosition();
			break;
		case MotionEvent.ACTION_UP: // get the motion of finger leave.
			updateViewPosition();
			mTouchX = mTouchY = 0;
			if ((x - mStartX) < 5 && (y - mStartY) < 5) {
				if (mClickListener != null) {
					mClickListener.onClick(this);
				}
			}
			break;
		}
		return true;
	}

	@Override
	public void setOnClickListener(OnClickListener l) {
		this.mClickListener = l;
	}

	private void updateViewPosition() {
		// update the window position
		windowManagerParams.x = (int) (x - mTouchX);
		windowManagerParams.y = (int) (y - mTouchY);
		windowManager.updateViewLayout(this, windowManagerParams); // refresh to show.
	}
}

代码解释： 
int statusBarHeight = frame.top; 
为获取状态栏的高度，为什么在event.getRawY()的时候减去状态栏的高度呢？ 
因为我们的悬浮窗口不可能显示到状态栏中去，而后getRawY为获取到屏幕原点的距离。当我们屏幕处于全屏模式时，获取到的状态栏高度会变成0 
(x - mStartX) < 5 && (y - mStartY) < 5 
如果我们在触摸过程中，移动距离少于5 ,则视为点击，触发点击的回调。 
另外我们需要自定义一个application: 

import android.app.Application;
import android.view.WindowManager;

public class FloatApplication extends Application {
	private WindowManager.LayoutParams windowParams = new WindowManager.LayoutParams();

	public WindowManager.LayoutParams getWindowParams() {
		return windowParams;
	}
}

代码解释： 
自定义application的目的是为了保存windowParams的值 ，因为我们在拖动悬浮窗口的时候，如果每次都重新new一个layoutParams的话，在update 
的时候会在异常发现。 
windowParams的值也不一定非得在自定义application里面来保存，只要是全局的都行。 
最后我们再来看看Activity中的实现：

import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.graphics.PixelFormat;
import android.view.Gravity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.view.WindowManager;
import android.view.WindowManager.LayoutParams;
import android.widget.Toast;

/**
 * @author torv
 *
 */
public class MainActivity extends Activity implements OnClickListener {
	private WindowManager windowManager = null;
	private WindowManager.LayoutParams windowManagerParams = null;
	private FloatView floatView = null;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		requestWindowFeature(Window.FEATURE_NO_TITLE);//cancel title bar
		getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
				WindowManager.LayoutParams.FLAG_FULLSCREEN);//full screen
		setContentView(R.layout.activity_main);
		createView();
	}

//	@Override
//	public boolean onCreateOptionsMenu(Menu menu) {
//		getMenuInflater().inflate(R.menu.activity_main, menu);
//		return true;
//	}

	public void onDestroy() {
		super.onDestroy();
		// destroy float window
		windowManager.removeView(floatView);
	}

	private void createView() {
		floatView = new FloatView((FloatApplication)getApplicationContext());
		floatView.setOnClickListener(this);
		floatView.setImageResource(R.drawable.ic_launcher); // use default icon.
		//get WindowManager
		windowManager = (WindowManager) getApplicationContext().getSystemService(Context.WINDOW_SERVICE);
		// set LayoutParams(global) params
		windowManagerParams = ((FloatApplication) getApplication()).getWindowParams();
		windowManagerParams.type = LayoutParams.TYPE_PHONE; // set window type
		windowManagerParams.format = PixelFormat.RGBA_8888; // set pic format, background transparent
		// set Window flag
		windowManagerParams.flags = LayoutParams.FLAG_NOT_TOUCH_MODAL|LayoutParams.FLAG_NOT_FOCUSABLE;
		/*
		 * PS: flag value should be： LayoutParams.FLAG_NOT_TOUCH_MODAL not effect event
		 * LayoutParams.FLAG_NOT_FOCUSABLE unable focus. LayoutParams.FLAG_NOT_TOUCHABLE
		 * unable touch focus.
		 */
		// adjust the window to left-top
		windowManagerParams.gravity = Gravity.LEFT | Gravity.TOP;
		// set x.y base on left-top
		windowManagerParams.x = 0;
		windowManagerParams.y = 0;
		// set float window height, weight.
		windowManagerParams.width = LayoutParams.WRAP_CONTENT;
		windowManagerParams.height = LayoutParams.WRAP_CONTENT;
		// show my float view.
		windowManager.addView(floatView, windowManagerParams);
	}

	public void onClick(View v) {
		Toast.makeText(this, "Clicked", Toast.LENGTH_SHORT).show();
	}
}

代码解释： 
在activity中我们主要是添加悬浮窗，并且设置他的位置。另外需要注意flags的应用： 
LayoutParams.FLAG_NOT_TOUCH_MODAL 不影响后面的事件 
LayoutParams.FLAG_NOT_FOCUSABLE 不可聚焦 
LayoutParams.FLAG_NOT_TOUCHABLE 不可触摸 
最后我们在onDestroy()中移除到悬浮窗口。所以，我们测试的时候，记得按Home键来切换到桌面。 
最后千万记得，在androidManifest.xml中来申明我们需要用到的android.permission.SYSTEM_ALERT_WINDOW权限 
并且记得申明我们自定义的application哦。 
AndroidManifest.xml代码如下： 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.torv.pro"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />
    
    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme"
        android:name="FloatApplication"> 
        <activity
            android:name="com.torv.pro.MainActivity"
            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>