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引用：http://zuoshu.iteye.com/blog/1505796

最近研究锁屏，按照常规的方法，常规方法如下

public void onAttachedToWindow()
{
       this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);
       super.onAttachedToWindow();
}

 但是这个方法到了4.0的系统上就失效了，按home照样会返回桌面。apktool了几个锁屏的软件之后发现其实现方法，即用WindowManager的addview方法将view加到窗口上，加上的时候将view的layoutparamas的type设为LayoutParams.TYPE_SYSTEM_ERROR，这个值sdk的解释为

public static final int TYPE_SYSTEM_ERROR
Since: API Level 1
Window type: internal system error windows, appear on top of everything they can.

 如果直接这样用会报错，还要在AndroidManifest.xml里面加上权限<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>，ok上完整代码，封装了一个类，其中Lock和hide方法实现锁屏和解锁。

public class LockLayer {
    private Activity mActivty;
    private WindowManager mWindowManager;
    private View mLockView;
    private LayoutParams mLockViewLayoutParams;

    public LockLayer(Activity act) {
        mActivty = act;
        init();
    }

    private void init(){
        mWindowManager = mActivty.getWindowManager();
        mLockViewLayoutParams = new LayoutParams();
        mLockViewLayoutParams.width = LayoutParams.MATCH_PARENT;
        mLockViewLayoutParams.height = LayoutParams.MATCH_PARENT;
        //实现关键
        mLockViewLayoutParams.type = LayoutParams.TYPE_SYSTEM_ERROR;
        //apktool value，这个值具体是哪个变量还请网友帮忙
        mLockViewLayoutParams.flags = 1280;
    }
    public void lock() {
        if(mLockView!=null){
            mWindowManager.addView(mLockView, mLockViewLayoutParams);
        }
    }
    public void unlock() {
        if(mWindowManager!=null){
            mWindowManager.removeView(mLockView);
        }
    }
    public void setLockView(View v){
        mLockView = v;
    }
}

 使用方法如下

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        View lock = View.inflate(this, R.layout.main, null);
        LockLayer lockLayer = new LockLayer(this);
        lockLayer.setLockView(lock);
        lockLayer.lock();
    }

ok,这时可以实现按home键不返回桌面的效果，其他的键需要用另外的代码实现，网上都有。这段代码只调用一次的时候没有问题，但是如果遇到多线程或者多次lock和hide就会有问题，修改如下，一是将LockLayer改为单例模式，二是在hide和lock的时候先判断状态。修改后代码如下

public class LockLayer {
    private Activity mActivty;
    private WindowManager mWindowManager;
    private View mLockView;
    private LayoutParams mLockViewLayoutParams;
    private static LockLayer mLockLayer;
    private boolean isLocked;

    public static synchronized LockLayer getInstance(Activity act){
        if(mLockLayer == null){
            mLockLayer = new LockLayer(act);
        }
        return mLockLayer;
    }

    private LockLayer(Activity act) {
        mActivty = act;
        init();
    }

    private void init(){
        isLocked = false;
        mWindowManager = mActivty.getWindowManager();
        mLockViewLayoutParams = new LayoutParams();
        mLockViewLayoutParams.width = LayoutParams.MATCH_PARENT;
        mLockViewLayoutParams.height = LayoutParams.MATCH_PARENT;
        //实现关键
        mLockViewLayoutParams.type = LayoutParams.TYPE_SYSTEM_ERROR;
        //apktool value，这个值具体是哪个变量还请网友帮忙
        mLockViewLayoutParams.flags = 1280;
    }
    public synchronized void lock() {
        if(mLockView!=null&&!isLocked){
            mWindowManager.addView(mLockView, mLockViewLayoutParams);
        }
        isLocked = true;
    }
    public synchronized void unlock() {
        if(mWindowManager!=null&&isLocked){
            mWindowManager.removeView(mLockView);
        }
        isLocked = false;
    }
    public synchronized void setLockView(View v){
        mLockView = v;
    }
}

 还有个问题是mLockViewLayoutParams.flags = 1280;1280这个值具体是哪个变量还不知道，有知道的留个言。

• LockScreen.zip (148.2 KB)
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