ViewDragHelper侧滑关闭再升级-仿微信

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/c__chao/article/details/82713957

继上篇文章Android 利用ViewDragHelper打造侧滑关闭控件，因为上次有事出门了，没有扩展这个功能，今天刚好周末有点时间，索性补上吧。

效果展示：

思路梳理：执行当前页面侧滑关闭的时候，需要上个页面同步滚动，从而达到联动的效果，联动效果很简单，使用属性动画即可，问题是怎么拿到上个页面的View？我们知道Activity可以拿到当前页面的View，所以我们需要拿到上个页面的Activity，那么有什么好的做法呢？这里提供两种方法：

• 1.在基类BaseActivity中将自己的实例保存下来。

• 2.使用Application提供的ActivityLifecycleCallbacks，在Activity创建时将实例保存。

我这里使用第二种方法：

import android.app.Activity;
import android.app.Application;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.View;

import java.util.Stack;

/**
 * Created by Chao on 2018-09-15.
 */

public class SwipeBackManager implements Application.ActivityLifecycleCallbacks {
    private Stack<Activity> mActivityStack = new Stack<>();
    private static final SwipeBackManager instance = new SwipeBackManager();

    private SwipeBackManager() {
    }

    public static SwipeBackManager getInstance() {
        return instance;
    }

    /**
     * 必须在 Application 的 onCreate 方法中调用
     */
    public void init(Application application) {
        application.registerActivityLifecycleCallbacks(this);
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle bundle) {
        //Activity创建时，将其保存。
        mActivityStack.add(activity);
    }

    @Override
    public void onActivityStarted(Activity activity) {

    }

    @Override
    public void onActivityResumed(Activity activity) {

    }

    @Override
    public void onActivityPaused(Activity activity) {

    }

    @Override
    public void onActivityStopped(Activity activity) {

    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle bundle) {

    }

    @Override
    public void onActivityDestroyed(Activity activity) {
        //Activity销毁时，将其移除。
        mActivityStack.remove(activity);
    }

    /**
     * 获取倒数第二个 Activity
     */
    @Nullable
    private Activity getPenultimateActivity() {
        Activity activity = null;
        try {
            if (mActivityStack.size() > 1) {
                activity = mActivityStack.get(mActivityStack.size() - 2);
            }
        } catch (Exception e) {
        }
        return activity;
    }

    /**
     * 暴露Activity滑动动画
     */
    public void onPanelSlide(float slideOffset) {
        try {
            Activity activity = getPenultimateActivity();
            if (activity != null) {
                View decorView = activity.getWindow().getDecorView();
                decorView.setTranslationX(-(decorView.getMeasuredWidth() - slideOffset) / 3);
            }
        } catch (Exception e) {
        }
    }

    /**
     * 暴露Activity关闭动画
     */
    public void onPanelClosed() {
        try {
            Activity activity = getPenultimateActivity();
            if (activity != null) {
                View decorView = activity.getWindow().getDecorView();
                decorView.setTranslationX(0);
            }
        } catch (Exception e) {
        }
    }
}

然后在Application中注册：

import android.app.Application;

import view.peakchao.view.view.SwipeBackManager;

/**
 * Created by Chao on 2018-09-15.
 */

public class App extends Application {

    @Override
    public void onCreate() {
        super.onCreate();
        SwipeBackManager.getInstance().init(this);
    }
}

在上篇文章中编写的SwipeBackLayout中进行调用：

import android.app.Activity;
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v4.widget.ViewDragHelper;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;

import view.peakchao.view.R;

/**
 * 基于ViewDragHelper的侧滑关闭View
 * Created by Chao on 2018-09-09.
 */

public class SwipeBackLayout extends FrameLayout {
    private ViewDragHelper mHelper;
    private Activity mActivity;
    private View mView;

    public SwipeBackLayout(@NonNull Context context) {
        super(context);
        initViewDragHelper();
    }


    /**
     * 绑定 Activity
     *
     * @param activity 容器 Activity
     */
    public void attachActivity(Activity activity) {
        mActivity = activity;
        ViewGroup decor = (ViewGroup) activity.getWindow().getDecorView();
        View content = decor.getChildAt(0);
        decor.removeView(content);
        mView = content;
        addView(content);
        decor.addView(this);
    }

    /**
     * 初始化方法
     */
    private void initViewDragHelper() {
        mHelper = ViewDragHelper.create(this, 1.0f, new ViewDragHelper.Callback() {
            @Override
            public boolean tryCaptureView(View child, int pointerId) {
                // 默认不扑获 View
                return false;
            }

            @Override
            public int clampViewPositionHorizontal(View child, int left, int dx) {
                // 拖动限制（大于左边界）
                SwipeBackManager.getInstance().onPanelSlide(left);
                return Math.max(0, left);
            }

            @Override
            public int clampViewPositionVertical(View child, int top, int dy) {
                //左右侧滑时，限制不能上下拖动。
                return 0;
            }

            @Override
            public void onViewReleased(View releasedChild, float xvel, float yvel) {
                // 拖动距离大于屏幕的一半右移，拖动距离小于屏幕的一半左移
                int left = releasedChild.getLeft();
                if (left > getWidth() / 2) {
                    if (mActivity != null) {
                        mActivity.finish();
                        mActivity.overridePendingTransition(0, R.anim.right_out);
                        SwipeBackManager.getInstance().onPanelClosed();
                    }
                } else {
                    mHelper.settleCapturedViewAt(0, 0);
                }
                invalidate();
            }

            @Override
            public void onEdgeDragStarted(int edgeFlags, int pointerId) {
                // 移动子 View
                mHelper.captureChildView(mView, pointerId);
            }
        });
        // 跟踪左边界拖动
        mHelper.setEdgeTrackingEnabled(ViewDragHelper.EDGE_LEFT);
    }


    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        // 拦截代理
        return mHelper.shouldInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        // Touch Event 代理
        mHelper.processTouchEvent(event);
        return true;
    }

    @Override
    public void computeScroll() {
        // 子 View 需要更新状态
        if (mHelper.continueSettling(true)) {
            invalidate();
        }
    }

}

在SwipeBackLayout中，我们只加入了两句代码，如下：

SwipeBackManager.getInstance().onPanelSlide(left);
SwipeBackManager.getInstance().onPanelClosed();

由于我本人只是喜欢写Demo玩，所以一般都以功能为主，其实可以添加更多的细节，不过我觉得没有多大意义，因为需求总是多变的，只要知道核心思想，改造将会轻而易举。