WindowManager
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我们Android平台是一个又一个的Activity组成的,每一个Activity有一个或者多个View构成。所以说,当我们想显示一个界面的时候,我们首先想到的是建立一个Activity,然后所有的操作在Activity里面实现,或者是一个Dialog或者Toast。这种方式固然简单,但是在有些情况下,我们要求的只是简单的显示,用Activity显然是多余,这个时候,我们如何处理呢?
原来,整个Android的窗口机制是基于一个叫做 WindowManager,这个接口可以添加view到屏幕,也可以从屏幕删除view。它面向的对象一端是屏幕,另一端就是View,直接忽略我们以前的Activity或者Dialog之类的东东。其实我们的Activity或者Diolog底层的实现也是通过WindowManager,这个 WindowManager是全局的,整个系统就是这个唯一的东东。它是显示View的最底层了。
一、一个简单WindowManager实例
1 package com.example.qjm3662.simplewindowsmanager; 2 3 import android.graphics.PixelFormat; 4 import android.support.v7.app.AppCompatActivity; 5 import android.os.Bundle; 6 import android.view.WindowManager; 7 import android.widget.TextView; 8 9 public class MainActivity extends AppCompatActivity {10 11 WindowManager wManager;12 @Override13 protected void onCreate(Bundle savedInstanceState) {14 super.onCreate(savedInstanceState);15 setContentView(R.layout.activity_main);16 17 //Activity自带一个getWindowManager()方法,可以获得当前系统的WindowManager18 wManager = getWindowManager();19 TextView tv = new TextView(this);20 tv.setText("sdgvsd");21 //布局参数22 WindowManager.LayoutParams params = new WindowManager.LayoutParams();23 params.width = 200;24 params.height = 200;25 26 //设置透明程度27 params.format = PixelFormat.TRANSPARENT;28 //params.format = PixelFormat.RGBA_8888;29 //设置是否获得焦点,如果获得焦点,则底层的View无法获得焦点,也无法响应返回键,默认是获得30 params.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE;31 wManager.addView(tv,params);32 }33 }
二、WindowManager的属性(WindowManager.LayoutParms)
详细的属性表在:
http://www.cnblogs.com/shitianzeng/articles/2814050.html
三、如何让一个view显示在桌面(即Activity销毁后(或在后台)仍可在桌面显示指定view)---》eg:各种安全软件的悬浮球
----》利用Service
1 package com.example.qjm3662.windowmanager; 2 3 import android.content.Intent; 4 import android.os.Bundle; 5 import android.support.v7.app.AppCompatActivity; 6 import android.view.Menu; 7 import android.view.MenuItem; 8 import android.view.View; 9 import android.widget.Button;10 11 public class MainActivity extends AppCompatActivity {12 13 Button button;14 @Override15 protected void onCreate(Bundle savedInstanceState) {16 super.onCreate(savedInstanceState);17 setContentView(R.layout.activity_main);18 19 button = (Button) findViewById(R.id.btn_start);20 button.setOnClickListener(new View.OnClickListener() {21 @Override22 public void onClick(View v) {23 startService(new Intent(MainActivity.this,WindowManagerService.class));24 }25 });26 }27 28 @Override29 public boolean onCreateOptionsMenu(Menu menu) {30 getMenuInflater().inflate(R.menu.menu_main,menu);31 return true;32 }33 34 @Override35 public boolean onOptionsItemSelected(MenuItem item) {36 int id = item.getItemId();37 38 if(id == R.id.action_settings){39 return true;40 }41 return super.onOptionsItemSelected(item);42 }43 }
package com.example.qjm3662.windowmanager;import android.app.Service;import android.content.Context;import android.content.Intent;import android.graphics.PixelFormat;import android.os.Handler;import android.os.IBinder;import android.view.Gravity;import android.view.LayoutInflater;import android.view.View;import android.view.WindowManager;import android.widget.TextView;public class WindowManagerService extends Service { private Handler handler = new Handler(); public WindowManagerService() { } @Override public IBinder onBind(Intent intent) { // TODO: Return the communication channel to the service. return null; } @Override public int onStartCommand(Intent intent, int flags, int startId) { String msg = "This is a text message"; final WindowManager wm = (WindowManager) getSystemService(Context.WINDOW_SERVICE); final View view = LayoutInflater.from(getApplicationContext()).inflate(R.layout.view_system,null); TextView tv = (TextView) view.findViewById(R.id.tv); tv.setText(msg); final WindowManager.LayoutParams params = new WindowManager.LayoutParams(); params.x = 0; params.y = 0; params.gravity = Gravity.RIGHT | Gravity.BOTTOM; params.width = 400; params.height = 400; params.type = WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY; params.format = PixelFormat.TRANSPARENT; params.flags |= WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN; wm.addView(view,params); new Thread(){ @Override public void run() { super.run(); try { Thread.sleep(15000); handler.post(new Runnable() { @Override public void run() { wm.removeViewImmediate(view); } }); } catch (InterruptedException e) { e.printStackTrace(); } } }.start(); return super.onStartCommand(intent, flags, startId); }}
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