android app背景的touch事件

android app背景的touch事件,在網路上有資料,整理一下

1.
AndroidManifest.xml要給權限,加入

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.yplin.myapplication11">
    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.VIBRATE" />


    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity11">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".floatActivity"></activity>
    </application>

</manifest>

2.
取得WindowManager(是一個更上層的obj,可google一下)
建立dunmmy view(空的view)
設置LayoutParams
根據LayoutParams將dummy view加mWindowManager

package com.example.yplin.myapplication11;

import android.graphics.PixelFormat;


import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;

import android.view.MotionEvent;
import android.view.View;

import android.view.WindowManager;
import android.widget.LinearLayout;

//繼承AppCompatActivityAppCompatActivity實做OnTouchListener

public class MainActivity11 extends AppCompatActivity implements   View.OnTouchListener {

    private LinearLayout lc=null;
    private CustomView1 canvas_view =null;
    @Override    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main11);
        lc=(LinearLayout)findViewById(R.id.view1);
        canvas_view = new CustomView1(this);
        Context mContext=getApplicationContext();
        // 取得WindowManagerWindowManager        

        WindowManager mWindowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
        //建立一個dummy的view        

        LinearLayout mDummyView = new LinearLayout(mContext);
        //新設置LayoutParams叫params,注意androidManifest.xml需給權限        

        WindowManager.LayoutParams params = new WindowManager.LayoutParams(
                1, /* width */                1, /* height */                

                WindowManager.LayoutParams.TYPE_PHONE,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE |
                WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL |
                WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
                PixelFormat.TRANSPARENT        );
        //可更改dummy view設置params        

        //mDummyView.setLayoutParams(params);        

        //dummy view設置touch傾聽事件        

        mDummyView.setOnTouchListener(this);
        //根據params將dummy view加mWindowManager

        mWindowManager.addView(mDummyView, params);
    }
    //實作OnTouchListener的onTouch傾聽事件方法    

        @Override    

        public boolean onTouch(View v, MotionEvent event) {
        //LinearLayout lc=(LinearLayout)findViewById(R.id.view1);        

        if(lc.indexOfChild(canvas_view)==-1) {

            lc.addView(canvas_view);
        }
        else        {
            lc.removeAllViews();
        }
        return false;
    }

    class CustomView1 extends View{

        Paint paint;

        public CustomView1(Context context) {
            super(context);
            paint = new Paint();                   //設置一新畫筆            

            paint.setColor(Color.RED);             //黄色            

            paint.setStrokeJoin(Paint.Join.ROUND);
            paint.setStrokeCap(Paint.Cap.ROUND);
            paint.setStrokeWidth(3);               //設置一筆刷大小3        }

        //create circle        

        @Override        

        protected void onDraw(Canvas canvas) {

            canvas.drawCircle(100, 100, 90, paint);

        }

    }
}

實際結果,背景下觸摸螢幕,touch事件被這app接收了