android handler原理

 

 

 

 

Handler的構造函數：

1、

 public Handler() {
        this(null, false);
    }

 2、

 public Handler(@Nullable Callback callback) {
        this(callback, false);
    }

3、

 public Handler(@NonNull Looper looper) {
        this(looper, null, false);
    }

4、

public Handler(@NonNull Looper looper, @Nullable Callback callback) {
        this(looper, callback, false);
    }

 

 

@UnsupportedAppUsage
    public Handler(@NonNull Looper looper, @Nullable Callback callback, boolean async) {
        mLooper = looper;
        mQueue = looper.mQueue;
        mCallback = callback;
        mAsynchronous = async;
    }