Android对话框之dismiss和cancel和hide区别

在我们看来两者效果都是一样的，其实看下源码就知道cancel肯定会去调dismiss的，如果调用的cancel的话就可以监听DialogInterface.OnCancelListener。

/**
     * Cancel the dialog.  This is essentially the same as calling {@link #dismiss()}, but it will
     * also call your {@link DialogInterface.OnCancelListener} (if registered).
     */
    public void cancel() {
        if (!mCanceled && mCancelMessage != null) {
            mCanceled = true;
            // Obtain a new message so this dialog can be re-used
            Message.obtain(mCancelMessage).sendToTarget();
        }
        dismiss();
    }

dismiss可以在任何线程调用，但是最好不要覆写dismiss方法，实在需要就在onStop里去override。

/**
     * Dismiss this dialog, removing it from the screen. This method can be
     * invoked safely from any thread.  Note that you should not override this
     * method to do cleanup when the dialog is dismissed, instead implement
     * that in {@link #onStop}.
     */
    @Override
    public void dismiss() {
        if (Looper.myLooper() == mHandler.getLooper()) {
            dismissDialog();
        } else {
            mHandler.post(mDismissAction);
        }
    }

在dismissDialog里调用了onStop

void dismissDialog() {
        if (mDecor == null || !mShowing) {
            return;
        }

        if (mWindow.isDestroyed()) {
            Log.e(TAG, "Tried to dismissDialog() but the Dialog‘s window was already destroyed!");
            return;
        }

        try {
            mWindowManager.removeViewImmediate(mDecor);
        } finally {
            if (mActionMode != null) {
                mActionMode.finish();
            }
            mDecor = null;
            mWindow.closeAllPanels();
            onStop();
            mShowing = false;

            sendDismissMessage();
        }
    }

补上hide方法，注释上说了hide只是隐藏了对话框并没有销毁，如果打算用这方法来灭掉对话框就会出现问题，在Activity销毁的时候就会出现崩溃日志了，因为

Activity销毁时是需要把对话框都关闭掉的。

日志如下：

android.view.WindowLeaked: Activity com.example.androidtest_progressdialog.MainActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView{434557e8 G.E..... R.....ID 0,0-1026,288} that was originally added here

再看一下hide里是做什么操作：

/**
     * Hide the dialog, but do not dismiss it.
     */
    public void hide() {
        if (mDecor != null) {
            mDecor.setVisibility(View.GONE);
        }
    }

可以看出，hide只是把对话框里的DecorView设置为不可见，并没有从Window移除掉这个DecorView。