Android小知识汇总

1、自定义应用标题

在Activity的onCreate方法中加入以下代码，顺序要注意，不然发现效果不对。

requestWindowFeature(Window.FEATURE_CUSTOM_TITLE); 
setContentView(R.layout.mainactivity);    //Activity的布局 
getWindow().setFeatureInt(Window.FEATURE_CUSTOM_TITLE,布局资源id);   //标题栏的布局 

2、关闭屏幕旋转。在AndroidManifest.xml注册Activity时加上后面两个属性。android:screenOrientation：屏幕方向。

<activity android:name=".FlowActivity" android:configChanges="keyboardHidden|orientation"
			android:screenOrientation="landscape" />

3、卸载应用。

    private void uninstallPkg(String packageName) {
        // Create new intent to launch Uninstaller activity
        Uri packageURI = Uri.parse("package:"+packageName);
        Intent uninstallIntent = new Intent(Intent.ACTION_DELETE, packageURI);
        startActivity(uninstallIntent);
        setIntentAndFinish(true, true);
    }

4、获得文件夹大小及可用空间，例：应用安装区大小。

String path = Environment.getDataDirectory().getPath();
StatFs stat = new StatFs(path);
long blockSize = stat.getBlockSize();
long totalBlocks = stat.getBlockCount();
long availableBlocks = stat.getAvailableBlocks();

5、关闭/恢复窗口动画，需要系统权限。

//关闭窗口动画
IWindowManager mWindowManager = IWindowManager.Stub.asInterface(ServiceManager
				.getService("window"));
float[] mAnimationScales;
		try {
			mAnimationScales = mWindowManager.getAnimationScales();//保存关闭之前窗口动画效果
			mWindowManager.setAnimationScales(new float[] { 0, 0 });
		} catch (RemoteException e) {
			e.printStackTrace();
		}
//恢复窗口动画
mWindowManager.setAnimationScales(mAnimationScales);

6、设置中如何跳转到应用详细信息界面。

Intent intent = new Intent(
	        Settings.ACTION_APPLICATION_DETAILS_SETTINGS,
		Uri.fromParts("package", 应用包名 , null));
// start new activity to display extended information
startActivityForResult(intent, 1);

7、屏幕旋转时不调用onCreate方法。

manifest.xml中注册activity时加入属性：android:configChanges="orientation|keyboardHidden"

Activity中重写onConfigurationChanged方法：

	@Override
	public void onConfigurationChanged(Configuration newConfig) {
		super.onConfigurationChanged(newConfig);
	}

8、安装应用

Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.parse("file://xxx.apk","application/vnd.android.package-archive");
startActivity(intent);

9、从应用进入主界面(Launcher)

Intent i = new Intent(Intent.ACTION_MAIN);
// i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); //如果是服务里调用，必须加入new task标识
i.addCategory(Intent.CATEGORY_HOME);
startActivity(i);

10、灭屏

try {
	IPowerManager power = IPowerManager.Stub.asInterface(
		 ServiceManager.getService("power"));
	if (power != null) {
		power.goToSleep(SystemClock.uptimeMillis());
	}
} catch (RemoteException doe) {  
} 

需要权限<uses-permission android:name="android.permission.DEVICE_POWER"/>

11、亮屏

PowerManager powerManager = (PowerManager)mContext.getSystemService(Context.POWER_SERVICE);
WakeLock wakeLock = powerManager.newWakeLock(PowerManager.FULL_WAKE_LOCK|PowerManager.ACQUIRE_CAUSES_WAKEUP,"");
wakeLock.acquire();

需要权限<uses-permission android:name="android.permission.WAKE_LOCK"/>

PARTIAL_WAKE_LOCK :保持CPU 运转，屏幕和键盘灯有可能是关闭的。

SCREEN_DIM_WAKE_LOCK ：保持CPU 运转，允许保持屏幕显示但有可能是灰的，允许关闭键盘灯

SCREEN_BRIGHT_WAKE_LOCK ：保持CPU 运转，允许保持屏幕高亮显示，允许关闭键盘灯

FULL_WAKE_LOCK ：保持CPU 运转，保持屏幕高亮显示，键盘灯也保持亮度

12、获取正在运行的程序所占内存大小（从设置中扒出来的代码）

		Debug.MemoryInfo[] mems;
		try {
			mems = ActivityManagerNative.getDefault()
			        .getProcessMemoryInfo(pids_array);
			int i = 0;
			for(Debug.MemoryInfo mem : mems){
				double mSize = ((double)mem.getTotalPss()) * 1024;			
				//System.out.println(pids_array[i] + " - " + mSize);
			}
		} catch (RemoteException e) {
			e.printStackTrace();
		}