扩展ImageView使可旋转

继承ImageView,增加angle属性，重写OnMeasure和OnDraw方法

package com.upon.common.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.widget.ImageView;

import com.upon.xxxx.R;

public class UponRotateImageView extends ImageView {

	private int mAngle;

	public UponRotateImageView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		loadAttributes(context, attrs);
	}

	public UponRotateImageView(Context context, AttributeSet attrs) {
		super(context, attrs);
		loadAttributes(context, attrs);
	}

	public UponRotateImageView(Context context) {
		super(context);
	}

	private void loadAttributes(Context context, AttributeSet attrs) {
		TypedArray arr = context.obtainStyledAttributes(attrs, R.styleable.RotateImageView);
		mAngle = arr.getInteger(R.styleable.RotateImageView_angle, 0);
		arr.recycle();
	}

	public int getAngle() {
		return mAngle;
	}

	public void setAngle(int angle) {
		mAngle = angle;
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		int w = getDrawable().getIntrinsicWidth();
		int h = getDrawable().getIntrinsicHeight();
		double a = Math.toRadians(mAngle);

		int width = (int) (Math.abs(w * Math.cos(a)) + Math.abs(h * Math.sin(a)));
		int height = (int) (Math.abs(w * Math.sin(a)) + Math.abs(h * Math.cos(a)));

		setMeasuredDimension(width, height);
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
	}

	@Override
	protected void onDraw(Canvas canvas) {
		canvas.save();
		canvas.rotate(mAngle % 360, getWidth() / 2, getHeight() / 2);
		getDrawable().draw(canvas);
		canvas.restore();
	}
}

attrs.xm文件中增加angle属性

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

</resources>

使用UponRotateImageView

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:upon="http://schemas.android.com/apk/res/com.upon.xxxx"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" >

    <com.upon.common.view.UponRotateImageView
        android:id="@+id/bkg_img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/conquer_nation_bkg"
        upon:angle="45" />

</RelativeLayout>