android前台渲染图片

android前台渲染，主要是重写view的ondraw方法，在canvas里操作

自定义MyView类

package com.ssln;import android.annotation.SuppressLint;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Matrix;import android.graphics.Paint;import android.util.AttributeSet;import android.view.View;public class MyView extends View {    private Bitmap bitmap;        //图片    private Paint paint;        //画笔    public MyView(Context context, AttributeSet attrs) {        super(context, attrs);        initBitmap();    }    /**     * 初始化信息     */    public void initBitmap()    {        //实例化画笔         paint=new Paint();                  //从资源中加载         bitmap=BitmapFactory.decodeResource(getResources(), R.drawable.img);    }    @SuppressLint("DrawAllocation")    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        paint.setAntiAlias(true);        //开启抗锯齿        paint.setColor(Color.BLACK);    //设置画笔颜色        paint.setTextScaleX(15);        //设置文字大小        canvas.drawBitmap(bitmap, 10,10, paint); //在10x10的位置画图片        canvas.save();                    //保存画布状态                Matrix m1=new Matrix();            //矩阵        m1.setTranslate(500, 10);        //平移 X500 Y10        Matrix m2=new Matrix();            m2.setRotate(15);                //旋转15°        Matrix m3=new Matrix();                    m3.setConcat(m1, m2);            //合并矩阵        m1.setScale(0.8f, 0.8f);        //设置缩放比例        m2.setConcat(m3, m1);            //合并        canvas.drawBitmap(bitmap, m2, paint);  //画图，经过了平移，旋转，缩放        canvas.restore();                //恢复画布状态        canvas.save();        paint.setAlpha(180);            //设置透明度        m1.setTranslate(200, 100);        m2.setScale(1.3f, 1.3f);        m3.setConcat(m1, m2);        canvas.drawBitmap(bitmap, m3, paint);  //画图，经过了平移，缩放        paint.reset();                  //重置画笔        canvas.restore();        paint.setTextSize(24);        paint.setColor(Color.BLACK);        canvas.drawText("图片宽度:"+bitmap.getWidth(), 20,240, paint); //写文字，图像的宽度        canvas.drawText("图片高度:"+bitmap.getHeight(), 20,270, paint);        paint.reset();        } }

修改activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context="com.ssln.MainActivity" >    <com.ssln.MyView        android:layout_width="fill_parent"        android:layout_height="fill_parent"         /></RelativeLayout>

运行效果如下

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