向左對齊的Gallery
阿新 • • 發佈:2019-01-04
轉載地址:http://www.eoeandroid.com/thread-158088-1-1.html
系統自帶的Gallery選中的item總是在元件的中間。但是有些時候我們需要把選中的元素放在左邊或者是Gallery一出來就要放在左邊。
修改Gallery靠左對齊的思路:
1、Gellary總是對center進行鎖定的,所以可以考慮修改它的center的位置,把center改成在left的位置就可以了。
Gallery中有個方法:
/** *@return The center of this Gallery. */ private int getCenterOfGallery() { return (getWidth() - mPaddingLeft -mPaddingRight) / 2 + mPaddingLeft; }
只可惜這個方法是private,所以沒有辦法重寫。那就把原始碼拷貝出來進行修改吧,但是當你拷貝處理的時候會發現很多的變數是沒有辦法用的,這是因為:
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.
這個很好理解,不作翻譯。
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.
這也很好理解,自己翻譯。
總結:Gallery的原始碼太過複雜所以這個方法只好放棄。
2、重寫Gallery。這個問題的關鍵是如何重寫,重寫什麼。
Gallery
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);
}
}