向左对齐的Gallery

系统自带的Gallery选中的item总是在组件的中间。但是有些时候我们需要把选中的元素放在左边或者是Gallery一出来就要放在左边。
修改Gallery靠左对齐的思路:
1、Gellary总是对center进行锁定的,所以可以考虑修改它的center的位置,把center改成在left的位置就可以了。
Gallery中有个方法:
/**
*@return The center of this Gallery.
*/
private int getCenterOfGallery() {
return (getWidth() - mPaddingLeft -mPaddingRight) / 2 + mPaddingLeft;
}
只可惜这个方法是private,所以没有办法重写。那就把源码拷贝出来进行修改吧,但是当你拷贝处理的时候会发现很多的变量是没有办法用的,这是因为:
a. @ViewDebug.ExportedProperty
This annotation can be used to markfields and methods to be dumped by the view server. Only non-void methods withno arguments can be annotated by this annotation.
这个很好理解,不作翻译。
b. {@hide}
Views which have been hidden or removedwhich need to be animated on their way out. This field should be made private,so it is hidden from the SDK.
这也很好理解,自己翻译。
总结:Gallery的源码太过复杂所以这个方法只好放弃。
2、重写Gallery。这个问题的关键是如何重写,重写什么。

Gallery其实只是显示了数据,那么我们不必把数据移动位置而把摄像机移动位置不就可以了吗?正是这样完成了Gallery的重写。代码如下:



package eoe.android.CustomGallery;

import android.R.attr;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Camera;
import android.graphics.Matrix;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Transformation;
import android.widget.Gallery;

public class GalleryFlow extends Gallery {

private Camera mCamera;
private int mWidth;
private int mPaddingLeft;
private boolean flag;
private static int firstChildWidth;
private static int firstChildPaddingLeft;
private int offsetX;

public GalleryFlow(Context context) {
super(context);
mCamera = new Camera();
this.setStaticTransformationsEnabled(true);
}

public GalleryFlow(Context context, AttributeSet attrs) {
super(context, attrs);
mCamera = new Camera();
setAttributesValue(context, attrs);
this.setStaticTransformationsEnabled(true);
}

public GalleryFlow(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mCamera = new Camera();
setAttributesValue(context, attrs);
this.setStaticTransformationsEnabled(true);
}

private void setAttributesValue(Context context, AttributeSet attrs) {
TypedArray typedArray = context.obtainStyledAttributes(attrs,
new int[] { attr.paddingLeft });
mPaddingLeft = typedArray.getDimensionPixelSize(0, 0);
typedArray.recycle();
}

protected boolean getChildStaticTransformation(View child, Transformation t) {
t.clear();
t.setTransformationType(Transformation.TYPE_MATRIX);
mCamera.save();
final Matrix imageMatrix = t.getMatrix();
if (flag) {
firstChildWidth = getChildAt(0).getWidth();
firstChildPaddingLeft = getChildAt(0).getPaddingLeft();
flag = false;
}
offsetX = firstChildWidth / 2 + firstChildPaddingLeft + mPaddingLeft
- mWidth / 2;
mCamera.translate(offsetX, 0f, 0f);
mCamera.getMatrix(imageMatrix);
mCamera.restore();
return true;
}


@Override
public boolean onTouchEvent(MotionEvent event) {
event.offsetLocation(-offsetX, 0);
return super.onTouchEvent(event);
}

protected void onSizeChanged(int w, int h, int oldw, int oldh) {
if (!flag) {
mWidth = w * 2;
getLayoutParams().width = mWidth;
flag = true;
}
super.onSizeChanged(w, h, oldw, oldh);
}
}

posted on 2014-04-20 21:43  clarenceV1  阅读(260)  评论(0编辑  收藏  举报

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