Android 背景图片的缩放
ONE Goal ,ONE Passion !
我们看到一些效果,控件中的背景图片会慢慢变大,但是控件不会随着图片的放大而变大.效果如下:
分析:
想让图片变大,而且控件本身大小不能改变,那么就要改变图片自身大小,而不能改变控件大小.
实现原理:
1,首先拿到我们要放大的图片bitmap.
2,使用Bitmap.createBitmap().创建一个bitmap的副本.
3,使用matrix去改变图片副本本身大小
4,使用ValueAnimator去根据变化率将副本绘制出来.
自定义View
public class ScaleImage extends View {
private Drawable background;
private Bitmap bitmapCopy;
float scal = 1f;
private float orgFrac = 1.3f;
private int widthSize;
private int heightSize;
private float downY;
private float downX;
public ScaleImage(Context context) {
this(context, null);
}
public ScaleImage(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public ScaleImage(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
widthSize = MeasureSpec.getSize(widthMeasureSpec);
heightSize = MeasureSpec.getSize(heightMeasureSpec);
}
@Override
protected void onDraw(final Canvas canvas) {
super.onDraw(canvas);
if (background != null) {
BitmapDrawable bd = (BitmapDrawable) background;
final Bitmap bitmap = bd.getBitmap();
final Matrix matrix = new Matrix();
bitmapCopy = Bitmap.createBitmap(bitmap, 0, 0,
bitmap.getWidth(), bitmap.getHeight(),
matrix, true);
matrix.setScale(orgFrac + scal, 1, bitmapCopy.getWidth() / 2, bitmapCopy.getHeight() / 2);
canvas.drawBitmap(bitmapCopy, matrix, null);
}
}
public void startScale(int drawableId) {
background = getResources().getDrawable(drawableId);
if (background == null) {
throw new RuntimeException("background must not null");
} else {
ValueAnimator animator = ValueAnimator.ofFloat(0, 1);
animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
float fraction = (float) animation.getAnimatedValue();
scal = (float) (0.5 * fraction);
invalidate();
}
});
animator.setDuration(5000);
animator.setInterpolator(new BounceInterpolator());
animator.start();
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
downY = event.getY();
downX = event.getX();
break;
case MotionEvent.ACTION_UP:
float upY = event.getY();
float upX = event.getX();
if (Math.abs(upY - downY) < 5 && Math.abs(upX - downX) < 5) {
listener.backgroundClick();
}
break;
}
return true;
}
onBackgroundCilckListener listener;
public void addBackgroundCilckListener(onBackgroundCilckListener listener) {
this.listener = listener;
}
public interface onBackgroundCilckListener {
void backgroundClick();
}
}
跑起来
image = (ScaleImage) findViewById(R.id.image);
image.startScale(R.drawable.parallax_img);
image.addBackgroundCilckListener(new ScaleImage.onBackgroundCilckListener() {
@Override
public void backgroundClick() {
}
});
小提琴家
matrix使用待续
好了.直接使用控件,我们将资源文件中的Drawable传入就可以了.
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