android - 开发 Android 主屏幕

Question

我正在开发具有主屏幕的应用程序。此主屏幕的行为应类似于 android 主屏幕，您可以通过将手指放在触摸屏上来在多个 View 之间切换。

解决方法很简单。我有 3 个 View 实例、右、左和当前 View 。我从之前初始化的 viewflipper 中获得了这些实例。因为我有一台 HTC G1，所以我的屏幕宽度为 320 像素，高度为 480 像素。

想象一下，当您触摸屏幕时，您捕获了一个向下 Action 事件的向下值。然后你移动你的手指，屏幕应该以完全相同的方式移动，所以你必须重新计算 View 的位置。到目前为止它对我有用，但我面临一个奇怪的问题。当您在不移动手指但将其在屏幕上停留不到一秒钟的情况下触摸右 View 时， View 会消失并显示左 View 。

这是我的代码:

public class MainActivity extends Activity implements OnTouchListener{

    private ViewFlipper vf;
    private float downXValue;
    private View view1, view2, view3;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        this.vf = (ViewFlipper) findViewById(R.id.flipper);

        if(this.vf != null){
             this.view1 = vf.getChildAt(0);
             this.view2 = vf.getChildAt(1);  
             this.view3 = vf.getChildAt(2);
             vf.setDisplayedChild(0);
         }      

         LinearLayout layMain = (LinearLayout) findViewById(R.id.layout_main);
         layMain.setOnTouchListener((OnTouchListener) this);
    }

    public boolean onTouch(View v, MotionEvent arg1) {

         final View currentView = vf.getCurrentView();
         final View leftView, rightView;

         if(currentView == view1){
             leftView = view3;
             rightView = view2;
         }else if(currentView == view2){
             leftView = view1;
             rightView = view3;
         }else if(currentView == view3){
             leftView = view2;
             rightView = view1;
         }else{
             leftView = null;
             rightView = null;
         }

         switch (arg1.getAction()){
            case MotionEvent.ACTION_DOWN:{
                this.downXValue = arg1.getX();
                break;
            }
            case MotionEvent.ACTION_UP:{
                float currentX = arg1.getX();            
                    if ((downXValue < currentX)){
                        if(currentView != view3){
                        float t3 = (320-(currentX-downXValue))/320;                             
                        this.vf.setInAnimation(AnimationHelper.inFromLeftAnimation(t3));
                        this.vf.setOutAnimation(AnimationHelper.outToRightAnimation(t3));
                        this.vf.showPrevious(); } 
                      }

                    if ((downXValue > currentX)){
                        if(currentView != view2){
                        float t = (320-(downXValue-currentX))/320;
                        this.vf.setInAnimation(AnimationHelper.inFromRightAnimation(t));
                        this.vf.setOutAnimation(AnimationHelper.outToLeftAnimation(t));
                        this.vf.showNext();}    
                    }                         
            }
            break;
            case MotionEvent.ACTION_MOVE:{

                leftView.setVisibility(View.VISIBLE);
                rightView.setVisibility(View.VISIBLE);

                float currentX = arg1.getX();     
                if(downXValue > currentX){  
                    if(currentView != view2){
                        currentView.layout((int) (currentX - downXValue),
                        currentView.getTop(),
                        (int) (currentX - downXValue) + 320,
                        currentView.getBottom()); 
                    }
                }

                if(downXValue < currentX){  
                    if(currentView != view3){
                        currentView.layout((int) (currentX - downXValue),
                        currentView.getTop(),
                        (int) (currentX - downXValue) + 320,
                        currentView.getBottom());


                    }
                }
                leftView.layout(currentView.getLeft()-320, leftView.getTop(),
                       currentView.getLeft(), leftView.getBottom());   

                rightView.layout(currentView.getRight(), rightView.getTop(), 
                        currentView.getRight() + 320, rightView.getBottom());
                }
            }

        return true;
    }

    public static class AnimationHelper {
          public static Animation inFromRightAnimation(float param) {
            Animation inFromRight = new TranslateAnimation(
            Animation.RELATIVE_TO_PARENT, +param,
            Animation.RELATIVE_TO_PARENT, 0.0f,
            Animation.RELATIVE_TO_PARENT, 0.0f,
            Animation.RELATIVE_TO_PARENT, 0.0f);
            inFromRight.setDuration(250);
            inFromRight.setInterpolator(new AccelerateInterpolator());
            return inFromRight;
          }

          public static Animation outToLeftAnimation(float param) {
            Animation outtoLeft = new TranslateAnimation(
            Animation.RELATIVE_TO_PARENT, 0.0f,
            Animation.RELATIVE_TO_PARENT, -param,
            Animation.RELATIVE_TO_PARENT, 0.0f,
            Animation.RELATIVE_TO_PARENT, 0.0f);
            outtoLeft.setDuration(250);
            outtoLeft.setInterpolator(new AccelerateInterpolator());
            return outtoLeft;
          }

          // for the next movement
          public static Animation inFromLeftAnimation(float param) {
            Animation inFromLeft = new TranslateAnimation(
            Animation.RELATIVE_TO_PARENT, -param,
            Animation.RELATIVE_TO_PARENT, 0.0f,
            Animation.RELATIVE_TO_PARENT, 0.0f,
            Animation.RELATIVE_TO_PARENT, 0.0f);
            inFromLeft.setDuration(250);
            inFromLeft.setInterpolator(new AccelerateInterpolator());
            return inFromLeft;
          }

          public static Animation outToRightAnimation(float param) {
            Animation outtoRight = new TranslateAnimation(
            Animation.RELATIVE_TO_PARENT, 0.0f,
            Animation.RELATIVE_TO_PARENT, +param,
            Animation.RELATIVE_TO_PARENT, 0.0f,
            Animation.RELATIVE_TO_PARENT, 0.0f);
            outtoRight.setDuration(250);
            outtoRight.setInterpolator(new AccelerateInterpolator());
            return outtoRight;
          }
        }

}

我认为这样的主屏幕是一个有趣的 UI 元素。

有什么想法吗？

Answer 1

编辑(2012 年 7 月 3 日):

由于似乎仍然有很多关于这个答案的观点和评论，我想我应该添加一个注释，即对于较新的 SDK，您现在应该使用 ViewPager而是具有相同的功能。该类也包含在Android Support library 中。因此您也可以使用它在早期的 Android 设备上运行。

编辑(2013 年 3 月 4 日):

既然还有人来这里，我也想说我把 ViewPager 放在一起，背景以较慢的速度移动，以产生视差效果。代码是here .

如果您真的想手动完成所有操作，原始答案在下面...

我想你可以在这里找到你要找的东西:http://www.anddev.org/why_do_not_these_codes_work-t4012.html

我在另一个项目中使用它来创建具有不同 View 的主屏幕。这直接来自 Android 启动器，在关注该线程后效果很好。

这是我的代码...首先是源代码

package com.matthieu.launcher;

import android.content.Context;
import android.util.Log;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewConfiguration;
import android.widget.Scroller;

public class DragableSpace extends ViewGroup {
    private Scroller mScroller;
    private VelocityTracker mVelocityTracker;

    private int mScrollX = 0;
    private int mCurrentScreen = 0;

    private float mLastMotionX;

    private static final String LOG_TAG = "DragableSpace";

    private static final int SNAP_VELOCITY = 1000;

    private final static int TOUCH_STATE_REST = 0;
    private final static int TOUCH_STATE_SCROLLING = 1;

    private int mTouchState = TOUCH_STATE_REST;

    private int mTouchSlop = 0;

    public DragableSpace(Context context) {
        super(context);
        mScroller = new Scroller(context);

        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();

        this.setLayoutParams(new ViewGroup.LayoutParams(
                    ViewGroup.LayoutParams.WRAP_CONTENT,
                    ViewGroup.LayoutParams.FILL_PARENT));
    }

    public DragableSpace(Context context, AttributeSet attrs) {
        super(context, attrs);
        mScroller = new Scroller(context);

        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();

        this.setLayoutParams(new ViewGroup.LayoutParams(
                    ViewGroup.LayoutParams.WRAP_CONTENT ,
                    ViewGroup.LayoutParams.FILL_PARENT));

        TypedArray a=getContext().obtainStyledAttributes(attrs,R.styleable.DragableSpace);
        mCurrentScreen = a.getInteger(R.styleable.DragableSpace_default_screen, 0);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        /*
         * This method JUST determines whether we want to intercept the motion.
         * If we return true, onTouchEvent will be called and we do the actual
         * scrolling there.
         */

        /*
         * Shortcut the most recurring case: the user is in the dragging state
         * and he is moving his finger. We want to intercept this motion.
         */
        final int action = ev.getAction();
        if ((action == MotionEvent.ACTION_MOVE)
                && (mTouchState != TOUCH_STATE_REST)) {
            return true;
                }

        final float x = ev.getX();

        switch (action) {
            case MotionEvent.ACTION_MOVE:
                /*
                 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check
                 * whether the user has moved far enough from his original down touch.
                 */

                /*
                 * Locally do absolute value. mLastMotionX is set to the y value
                 * of the down event.
                 */
                final int xDiff = (int) Math.abs(x - mLastMotionX);

                boolean xMoved = xDiff > mTouchSlop;

                if (xMoved) {
                    // Scroll if the user moved far enough along the X axis
                    mTouchState = TOUCH_STATE_SCROLLING;
                }
                break;

            case MotionEvent.ACTION_DOWN:
                // Remember location of down touch
                mLastMotionX = x;

                /*
                 * If being flinged and user touches the screen, initiate drag;
                 * otherwise don't.  mScroller.isFinished should be false when
                 * being flinged.
                 */
                mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;
                break;

            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_UP:
                // Release the drag
                mTouchState = TOUCH_STATE_REST;
                break;
        }

        /*
         * The only time we want to intercept motion events is if we are in the
         * drag mode.
         */
        return mTouchState != TOUCH_STATE_REST;
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        if (mVelocityTracker == null) {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(event);

        final int action = event.getAction();
        final float x = event.getX();

        switch (action) {
            case MotionEvent.ACTION_DOWN:
                Log.i(LOG_TAG, "event : down");
                /*
                 * If being flinged and user touches, stop the fling. isFinished
                 * will be false if being flinged.
                 */
                if (!mScroller.isFinished()) {
                    mScroller.abortAnimation();
                }

                // Remember where the motion event started
                mLastMotionX = x;
                break;
            case MotionEvent.ACTION_MOVE:
                // Log.i(LOG_TAG,"event : move");
                // if (mTouchState == TOUCH_STATE_SCROLLING) {
                // Scroll to follow the motion event
                final int deltaX = (int) (mLastMotionX - x);
                mLastMotionX = x;

                //Log.i(LOG_TAG, "event : move, deltaX " + deltaX + ", mScrollX " + mScrollX);

                if (deltaX < 0) {
                    if (mScrollX > 0) {
                        scrollBy(Math.max(-mScrollX, deltaX), 0);
                    }
                } else if (deltaX > 0) {
                    final int availableToScroll = getChildAt(getChildCount() - 1)
                        .getRight()
                        - mScrollX - getWidth();
                    if (availableToScroll > 0) {
                        scrollBy(Math.min(availableToScroll, deltaX), 0);
                    }
                }
                // }
                break;
            case MotionEvent.ACTION_UP:
                Log.i(LOG_TAG, "event : up");
                // if (mTouchState == TOUCH_STATE_SCROLLING) {
                final VelocityTracker velocityTracker = mVelocityTracker;
                velocityTracker.computeCurrentVelocity(1000);
                int velocityX = (int) velocityTracker.getXVelocity();

                if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {
                    // Fling hard enough to move left
                    snapToScreen(mCurrentScreen - 1);
                } else if (velocityX < -SNAP_VELOCITY
                        && mCurrentScreen < getChildCount() - 1) {
                    // Fling hard enough to move right
                    snapToScreen(mCurrentScreen + 1);
                } else {
                    snapToDestination();
                }

                if (mVelocityTracker != null) {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
                // }
                mTouchState = TOUCH_STATE_REST;
                break;
            case MotionEvent.ACTION_CANCEL:
                Log.i(LOG_TAG, "event : cancel");
                mTouchState = TOUCH_STATE_REST;
        }
        mScrollX = this.getScrollX();

        return true;
    }

    private void snapToDestination() {
        final int screenWidth = getWidth();
        final int whichScreen = (mScrollX + (screenWidth / 2)) / screenWidth;
        Log.i(LOG_TAG, "from des");
        snapToScreen(whichScreen);
    }

    public void snapToScreen(int whichScreen) {         
        Log.i(LOG_TAG, "snap To Screen " + whichScreen);
        mCurrentScreen = whichScreen;
        final int newX = whichScreen * getWidth();
        final int delta = newX - mScrollX;
        mScroller.startScroll(mScrollX, 0, delta, 0, Math.abs(delta) * 2);             
        invalidate();
    }

    public void setToScreen(int whichScreen) {
        Log.i(LOG_TAG, "set To Screen " + whichScreen);
        mCurrentScreen = whichScreen;
        final int newX = whichScreen * getWidth();
        mScroller.startScroll(newX, 0, 0, 0, 10);             
        invalidate();
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        int childLeft = 0;

        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() != View.GONE) {
                final int childWidth = child.getMeasuredWidth();
                child.layout(childLeft, 0, childLeft + childWidth, child
                        .getMeasuredHeight());
                childLeft += childWidth;
            }
        }

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        final int width = MeasureSpec.getSize(widthMeasureSpec);
        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        if (widthMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException("error mode.");
        }

        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        if (heightMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException("error mode.");
        }

        // The children are given the same width and height as the workspace
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
        }
        Log.i(LOG_TAG, "moving to screen "+mCurrentScreen);
        scrollTo(mCurrentScreen * width, 0);      
    }  

    @Override
    public void computeScroll() {
        if (mScroller.computeScrollOffset()) {
            mScrollX = mScroller.getCurrX();
            scrollTo(mScrollX, 0);
            postInvalidate();
        }
    }
}

还有布局文件:

<?xml version="1.0" encoding="utf-8"?>
<com.matthieu.launcher.DragableSpace xmlns:app="http://schemas.android.com/apk/res/com.matthieu.launcher"
    xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/space"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
app:default_screen="1"
>
<include android:id="@+id/left"  layout="@layout/left_screen" />
<include android:id="@+id/center"  layout="@layout/initial_screen" />
<include android:id="@+id/right"  layout="@layout/right_screen" />
</com.matthieu.launcher.DragableSpace>

为了能够在 xml 文件中拥有额外的属性，您希望将其保存在 res/values/attrs.xml 中

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="DragableSpace">
        <attr name="default_screen" format="integer"/>
    </declare-styleable>
</resources>