我想要的是背景图片，其行为类似于股票主屏幕或天气应用程序：https://youtube.com/watch?v=i2Oh4GL5wBE#t=0m54s
我只需要一个没有动画的背景图像（就像那个视频中的道路一样），它会在滑动到另一个视图时“滚动一下”。 在我的应用程序中，我想通过滚动背景来浏览一些ListView。
我测试了什么：
两者都有效，但这需要一个非常大的图像，我不确定它是否可以正确缩放到不同的屏幕尺寸。此外，它的行为与原始主屏幕不同，后台在前景变为下一个视图时会稍微移动。
我检查了推荐的Launcher.java，它引导我进入了Workspace.java：
据我所知，它通过设置偏移来使用WallpaperManager。
mWallpaperManager.setWallpaperOffsets(getWindowToken(),
Math.max(0.f, Math.min(mScrollX/(float)scrollRange, 1.f)), 0);
API说：
setWallpaperOffsets（的IBinder windowToken，float xOffset，float Y偏移） 设置的位置 任何更大的当前壁纸 空间，当壁纸可见时 在给定的窗口后面。
但据我了解，这只会改变手机本身的背景图像。
我该怎么办？您是否知道开源应用程序或示例代码也是如此？ 可能我必须自己绘制画布（以前从未做过）。请给我一些建议。
答案 0 :(得分：10)
最后，我让它工作（仍然需要一些修改）。 ：）
我必须承认我无法在ViewGroup本身中绘制背景。嗯，它工作，但我无法控制滚动（滚动太多）。
我基本上做的是合并2个教程。
onDraw，如建议的那样）。我将符号缩减为单个符号，并将其从ImageView更改为LinearLayout。在该布局中我添加了ViewGroup，在onTouchEvent和onInterceptTouchEvent中做了一些小的更改，添加了一些不良代码，最后它起作用了。 ：）
如果有人感兴趣，我会清理代码并在此发布，但我对我的编码风格感到羞耻，这是一团糟。 ;）
非常感谢，感谢您的帮助！ ：）
<强>更新 所以，这是代码：
<强> MainActivity.java
package de.android.projects;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
<强> MoveBackground.java
package de.android.projects;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.widget.LinearLayout;
/*
* LinearLayout which moves the background image by touchEvents.
* Taken from: http://eagle.phys.utk.edu/guidry/android/DraggableSymbols.html
* and changed a little bit
*/
public class MoveBackground extends LinearLayout{
private Drawable background; // background picture
private float X = -300; // Current x coordinate, upper left corner - 300
private int scroll;
public MoveBackground(Context context) {
super(context);
}
public MoveBackground(Context context, AttributeSet attrs) {
super(context);
background = context.getResources().getDrawable(R.drawable.backgroundpicture);
//just for tests, not really optimized yet :)
background.setBounds(0,0,1000,getResources().getDisplayMetrics().heightPixels);
setWillNotDraw(false);
}
/*
* Don't need these methods, maybe later for gesture improvements
*/
/*
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
onTouchEvent(ev);
return false;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
final int action = ev.getAction();
switch (action) {
// MotionEvent class constant signifying a finger-drag event
case MotionEvent.ACTION_MOVE: {
// Request a redraw
invalidate();
break;
}
// MotionEvent class constant signifying a finger-up event
case MotionEvent.ACTION_UP:
invalidate(); // Request redraw
break;
}
return true;
}
*/
// This method will be called each time the screen is redrawn.
// When to redraw is under Android control, but we can request a redraw
// using the method invalidate() inherited from the View superclass.
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
// get the object movement
if (BadScrollHelp.getScrollX() != scroll){
//reduce the scrolling
X -= scroll / 5;
scroll = BadScrollHelp.getScrollX();
}
// Draw background image at its current locations
canvas.save();
canvas.translate(X,0);
background.draw(canvas);
canvas.restore();
}
}
<强> ViewFlipper.java
package de.android.projects;
import android.content.Context;
import android.os.Parcel;
import android.os.Parcelable;
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;
/*
* Flip different views. Taken from tutorial there http://android-projects.de/2011/01/04/android-homescreen-view-flipper/
*/
public class ViewFlipper 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 ViewFlipper(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));
setWillNotDraw(false);
requestDisallowInterceptTouchEvent(true);
}
public ViewFlipper(Context context, AttributeSet attrs) {
super(context, attrs);
TypedArray a = getContext().obtainStyledAttributes(attrs, R.styleable.DragableSpace);
mCurrentScreen = a.getInteger(R.styleable.DragableSpace_default_screen, 0);
mScroller = new Scroller(context);
mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
this.setLayoutParams(new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT ,
ViewGroup.LayoutParams.FILL_PARENT));
setWillNotDraw(false);
requestDisallowInterceptTouchEvent(true);
}
@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 + 50;
if (xMoved) {
// Scroll if the user moved far enough along the X axis then
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:
// Scroll to follow the motion event
final int deltaX = (int) (mLastMotionX - x);
mLastMotionX = x;
if (deltaX < 0) {
if (mScrollX > 0) {
BadScrollHelp.setScrollX(deltaX);
scrollBy(Math.max(-mScrollX, deltaX), 0);
}
} else if (deltaX > 0) {
final int availableToScroll = getChildAt(getChildCount() - 1)
.getRight()
- mScrollX - getWidth();
if (availableToScroll > 0) {
BadScrollHelp.setScrollX(deltaX);
scrollBy(Math.min(availableToScroll, deltaX), 0);
}
}
// Request a redraw
invalidate();
break;
case MotionEvent.ACTION_UP:
Log.i(LOG_TAG, "event : up");
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;
//neu unten
invalidate(); // Request redraw
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;
BadScrollHelp.setCurrentScreen(mCurrentScreen);
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;
BadScrollHelp.setCurrentScreen(mCurrentScreen);
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();
}
}
/**
* Return the parceable instance to be saved
*/
@Override
protected Parcelable onSaveInstanceState() {
final SavedState state = new SavedState(super.onSaveInstanceState());
state.currentScreen = mCurrentScreen;
return state;
}
/**
* Restore the previous saved current screen
*/
@Override
protected void onRestoreInstanceState(Parcelable state) {
SavedState savedState = (SavedState) state;
super.onRestoreInstanceState(savedState.getSuperState());
if (savedState.currentScreen != -1) {
mCurrentScreen = savedState.currentScreen;
BadScrollHelp.setCurrentScreen(mCurrentScreen);
}
}
// ========================= INNER CLASSES ==============================
public interface onViewChangedEvent{
void onViewChange (int currentViewIndex);
}
/**
* A SavedState which save and load the current screen
*/
public static class SavedState extends BaseSavedState {
int currentScreen = -1;
/**
* Internal constructor
*
* @param superState
*/
SavedState(Parcelable superState) {
super(superState);
}
/**
* Private constructor
*
* @param in
*/
private SavedState(Parcel in) {
super(in);
currentScreen = in.readInt();
}
/**
* Save the current screen
*/
@Override
public void writeToParcel(Parcel out, int flags) {
super.writeToParcel(out, flags);
out.writeInt(currentScreen);
}
/**
* Return a Parcelable creator
*/
public static final Parcelable.Creator<SavedState> CREATOR = new Parcelable.Creator<SavedState>() {
public SavedState createFromParcel(Parcel in) {
return new SavedState(in);
}
public SavedState[] newArray(int size) {
return new SavedState[size];
}
};
}
}
<强> BadScrollHelp.java
package de.android.projects;
public class BadScrollHelp {
private static int scrollX = 0;
private static int currentScreen = 0;
public static synchronized void setScrollX(int scroll){
scrollX = scroll;
}
public static synchronized void setCurrentScreen(int screen){
currentScreen = screen;
}
public static synchronized int getScrollX(){
return scrollX;
}
public static synchronized int getCurrentScreen(){
return currentScreen;
}
}
<强> main.xml中
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<de.android.projects.MoveBackground
xmlns:app="http://schemas.android.com/apk/res/de.android.projects"
android:id="@+id/space1"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<de.android.projects.ViewFlipper
xmlns:app="http://schemas.android.com/apk/res/de.android.projects"
android:id="@+id/space"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
app:default_screen="0" >
<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" />
</de.android.projects.ViewFlipper>
</de.android.projects.MoveBackground>
</FrameLayout>
left_screen.xml，right_screen.xml和initial_screen.xml
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:background="#00000000"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<LinearLayout android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<Button android:layout_width="100dip"
android:layout_height="50dip"
android:text="Button" />
</LinearLayout>
</LinearLayout>
attrs.xml（在值文件夹中）
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="DragableSpace">
<attr name="default_screen" format="integer"/>
</declare-styleable>
</resources>
所以，最后，就是这样。 onDraw方法仍需要进行一些修改。
到目前为止，我对此解决方案不满意，因为我认为必须可以在onDraw中使用ViewGroup方法。但我无法理解。
此外，使用静态方法设置变量似乎是一个肮脏的技巧。
如果有人可以告诉我如何将这些事件从ViewFlipper传递到父MoveBackground课程，我会很高兴。或者如何将MoveBackground绘图方法包含到ViewFlipper。
我可以将ViewFlipper类集成到MoveBackground类中，并以编程方式执行addView(viewFlipper)。比我不再需要那个静态解决方法了。 ：）
答案 1 :(得分：10)
答案 2 :(得分：5)
实现此目的的最简单方法是在传递给onDraw(Canvas)的Canvas上自己绘制图像。这是Launcher在介绍壁纸偏移API之前所做的事。
答案 3 :(得分：0)
非常有用的解决方案Rainer，非常感谢，这真的很有帮助，但我注意到了
Drawable.draw(canvas)
非常慢
Canvas.drawBitmap(bitmap,srcRect,dstRect,mPaint)
尝试一下！