Android - 解决Fragment + ViewPager的生命周期问题

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/biezhihua/article/details/83304771

public class FragmentVisibleHelper implements LifecycleObserver {

    private static final String TAG = "VisibleHelper";

    public interface IVisibleListener {

        void onVisible();

        void onInVisible();
    }

    boolean mIsVisibleToUser;
    boolean mStarted = false;

    volatile boolean mIsCalledVisible = false;
    volatile boolean mIsCalledInvisible = false;


    IVisibleListener mListener;

    public void setListener(IVisibleListener mListener) {
        this.mListener = mListener;
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    void onResume() {
        Log.d(TAG, String.format("%-60s %s", this.toString(), "onResume() called："));
        if (mIsVisibleToUser) {
            dispatchVisible();
        }
    }

    private void dispatchVisible() {
        Log.d(TAG, String.format("%-60s %s", this.toString(), "dispatchVisible() called mIsCalledVisible = [" + mIsCalledVisible + "] mIsCalledInvisible = [" + mIsCalledInvisible + "] "));
        if (!mIsCalledVisible) {
            mIsCalledVisible = true;
            mIsCalledInvisible = false;

            if (Profile.LOG) {
                Log.d(TAG, String.format("%-60s %s", this.toString(), "dispatchVisible() called onVisible"));
            }

            if (mListener != null) {
                mListener.onVisible();
            }
        }
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    void onPause() {
        Log.d(TAG, String.format("%-60s %s", this.toString(), "onPause() called："));
        if (mIsVisibleToUser) {
            dispatchInvisible();
        }
    }

    private void dispatchInvisible() {
        Log.d(TAG, String.format("%-60s %s", this.toString(), "dispatchInvisible() called mIsCalledVisible = [" + mIsCalledVisible + "] mIsCalledInvisible = [" + mIsCalledInvisible + "] "));
        if (!mIsCalledInvisible) {
            mIsCalledInvisible = true;
            mIsCalledVisible = false;

            if (Profile.LOG) {
                Log.d(TAG, String.format("%-60s %s", this.toString(), "dispatchInvisible() called onInVisible"));
            }

            if (mListener != null) {
                mListener.onInVisible();
            }
        }
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    void onStart() {
        Log.d(TAG, String.format("%-60s %s", this.toString(), "onStart() called"));
        mStarted = true;
        if (mIsVisibleToUser) {
            dispatchVisible();
        }
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    void onStop() {
        Log.d(TAG, String.format("%-60s %s", this.toString(), "onStop() called"));
        if (mIsVisibleToUser) {
            dispatchInvisible();
        }
        mStarted = false;
    }

    public void setUserVisibleHint(boolean isVisibleToUser) {
        Log.d(TAG, String.format("%-60s %s", this.toString(), "setUserVisibleHint() called with: isVisibleToUser = [" + isVisibleToUser + "]："));
        mIsVisibleToUser = isVisibleToUser;
        if (mStarted) { // fragment have created
            if (mIsVisibleToUser) {
                dispatchVisible();
            } else {
                dispatchInvisible();
            }
        }
    }

    public boolean isVisibleToUser() {
        return mIsVisibleToUser;
    }
}