Android侧滑返回的实现

IOS有侧滑回退的功能，可以侧滑回退到上一个Activity，并且在侧滑时，底层的actvity是透明显示的。下面代码将实现该功能。
主要实现思路是让Activity的整个容器滑动。

package com.tjpld.tonglingsafetyandroid.customview;import java.util.LinkedList;import java.util.List;import android.app.Activity;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.Rect;import android.graphics.drawable.Drawable;import android.support.v4.view.ViewPager;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.widget.FrameLayout;import android.widget.Scroller;import com.tjpld.tonglingsafetyandroid.R;public class SwipeBackLayout extends FrameLayout {    private static final String TAG = SwipeBackLayout.class.getSimpleName();    //放置Activity的View    private View mContentView;    //侧滑最小距离    private int mTouchSlop;    //按下的位置    private int downX;    private int downY;    //当前的位置    private int tempX;    private Scroller mScroller;    private int viewWidth;    //判断是否为滑动    private boolean isSilding;    //是否完成    private boolean isFinish;    //侧滑的阴影效果    private Drawable mShadowDrawable;    private Activity mActivity;    private List<ViewPager> mViewPagers = new LinkedList<ViewPager>();    public SwipeBackLayout(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public SwipeBackLayout(Context context, AttributeSet attrs, int defStyle) {        super(context, attrs, defStyle);        //得到最小的距离        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();        //初始化滑动对象        mScroller = new Scroller(context);        //初始化阴影资源        mShadowDrawable = getResources().getDrawable(R.drawable.shadow_left);    }    //对外部提供的接口    public void attachToActivity(Activity activity) {        mActivity = activity;        TypedArray a = activity.getTheme().obtainStyledAttributes(                new int[]{android.R.attr.windowBackground});        int background = a.getResourceId(0, 0);        a.recycle();  //从外界传入的activity页面的底层容器，setContentView设置的View的父容   器  父容器一般都是ViewGroup        ViewGroup decor = (ViewGroup) activity.getWindow().getDecorView();        //得到setContentView设置的View ViewGroup decorChild = (ViewGroup) decor.getChildAt(0);//设置它的背景色       decorChild.setBackgroundResource(background);        //移除到之前父容器中的布局view        decor.removeView(decorChild);        //为当前页面父容器添加设置过背景色后的子view        addView(decorChild);        setContentView(decorChild);        decor.addView(this);    }    //得到从外部传入的activity的布局容器    private void setContentView(View decorChild) {              mContentView = (View) decorChild.getParent();    }    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        ViewPager mViewPager = getTouchViewPager(mViewPagers, ev);        Log.i(TAG, "mViewPager = " + mViewPager);        //判断是否拦截此次事件        if (mViewPager != null && mViewPager.getCurrentItem() != 0) {            return super.onInterceptTouchEvent(ev);        }        switch (ev.getAction()) {            //当只是按下去是，既非滑动事件，不对此事件做处理            case MotionEvent.ACTION_DOWN:                downX = tempX = (int) ev.getRawX();                downY = (int) ev.getRawY();                break;            //当移动时拦截次事件 调用onTouchEvent            case MotionEvent.ACTION_MOVE:                int moveX = (int) ev.getRawX(); //如果滑动的位置到我按下的位置之间的距离大于系统默认的最小距离 视为一次滑动                if (moveX - downX > mTouchSlop                        && Math.abs((int) ev.getRawY() - downY) < mTouchSlop) {                    return true;                }                break;        }        return super.onInterceptTouchEvent(ev);    }    @Override    public boolean onTouchEvent(MotionEvent event) {    switch (event.getAction()) {      case MotionEvent.ACTION_MOVE:       //点击事件发生的位置       int moveX = (int) event.getRawX();       //滑动的距离，tempX当前的位置，在拦截事件里进行了初始化，第一次是你按下的位置       int deltaX = tempX - moveX;       //当前位置就是view滑动后的位置       tempX = moveX;       //如果滑动后的位置到按下的位置 大于默认滑动距离 视为一次滑动      if (moveX - downX > mTouchSlop && Math.abs((int) event.getRawY() - downY) < mTouchSlop) {                isSilding = true;                }  //如果是一次滑动的话，就让整个容器滑动  if (moveX - downX >= 0 && isSilding) {        mContentView.scrollBy(deltaX, 0);                }                break;            case MotionEvent.ACTION_UP:                isSilding = false;      //向右滑动，值是负的 所以是小于等于整个view的宽的1/2时 代表完成了一次滑动 触发事件                if (mContentView.getScrollX() <= -viewWidth / 2) {                    isFinish = true;                    scrollRight();                } else {                    scrollOrigin();                    isFinish = false;                }                break;        }        return true;    }    private void getAlLViewPager(List<ViewPager> mViewPagers, ViewGroup parent) {        int childCount = parent.getChildCount();        for (int i = 0; i < childCount; i++) {            View child = parent.getChildAt(i);            if (child instanceof ViewPager) {                mViewPagers.add((ViewPager) child);            } else if (child instanceof ViewGroup) {                getAlLViewPager(mViewPagers, (ViewGroup) child);            }        }    }    private ViewPager getTouchViewPager(List<ViewPager> mViewPagers, MotionEvent ev) {        if (mViewPagers == null || mViewPagers.size() == 0) {            return null;        }        Rect mRect = new Rect();        for (ViewPager v : mViewPagers) {            v.getHitRect(mRect);            if (mRect.contains((int) ev.getX(), (int) ev.getY())) {                return v;            }        }        return null;    }    @Override    protected void onLayout(boolean changed, int l, int t, int r, int b) {        super.onLayout(changed, l, t, r, b);        if (changed) {            viewWidth = this.getWidth();            getAlLViewPager(mViewPagers, this);            Log.i(TAG, "ViewPager size = " + mViewPagers.size());        }    }    @Override    protected void dispatchDraw(Canvas canvas) {        super.dispatchDraw(canvas);        if (mShadowDrawable != null && mContentView != null) {            int left = mContentView.getLeft()                    - mShadowDrawable.getIntrinsicWidth();            int right = left + mShadowDrawable.getIntrinsicWidth();            int top = mContentView.getTop();            int bottom = mContentView.getBottom();            mShadowDrawable.setBounds(left, top, right, bottom);            mShadowDrawable.draw(canvas);        }    }   //当滑动布局超过1/2抬手时,用户抬手，但用户认为这样算是完成了操作，接下来隐藏另一部分contentView的工作由系统完成    private void scrollRight() {   //计算出剩余的宽度 向右换滑动mContentView.getScrollX()负值        final int delta = (viewWidth + mContentView.getScrollX());//参数，起止X，起止Y，目标X，目标Y，持续时间//同时会调用computeScoller共同完成滑动       mScroller.startScroll(mContentView.getScrollX(), 0, -delta + 1, 0,                Math.abs(delta));        postInvalidate();    }    private void scrollOrigin() {        int delta = mContentView.getScrollX();        mScroller.startScroll(mContentView.getScrollX(), 0, -delta, 0,                Math.abs(delta));        postInvalidate();    }    @Override    public void computeScroll() {        if (mScroller.computeScrollOffset()) {           mContentView.scrollTo(mScroller.getCurrX(), mScroller.getCurrY());            postInvalidate();       //完成滑动时销毁页面            if (mScroller.isFinished() && isFinish) {                mActivity.finish();            }        }    }}

使用的时候让Activity继承SwipeBackActivity 这是一个空实现的Activity

public class SwipeBackActivity extends AppCompatActivity {    protected SwipeBackLayout layout;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        layout = (SwipeBackLayout) LayoutInflater.from(this).inflate(                R.layout.base, null);        layout.attachToActivity(this);    }    @Override    public void startActivity(Intent intent) {        super.startActivity(intent);        overridePendingTransition(R.anim.base_slide_right_in, R.anim.base_slide_remain);    }    // Press the back button in mobile phone    @Override    public void onBackPressed() {        super.onBackPressed();        overridePendingTransition(0, R.anim.base_slide_right_out);        //第一动画代表下一个即将出来的页的进入动画效果，第二个代表当前页的退出动画效果//      overridePendingTransition(R.anim.base_slide_right_in,R.anim.base_slide_left_out );    }}

注意：在style中设置activity的容器层的（window层）ViewGroup的背景为透明

    <style name="Theme.AppCompat.Translucent" parent="AppTheme">        <item name="android:windowBackground">@android:color/transparent</item>        <item name="android:colorBackgroundCacheHint">@null</item>        <item name="android:windowIsTranslucent">true</item>        <item name="android:windowAnimationStyle">@android:style/Animation</item>    </style>

同时给activity的layout布局View设置背景background.否则会使整个页面为透明