Android多媒体入门-如何绘制一张图

开始认真学一下Android多媒体开发，拓宽多媒体的技术面，绘制一张图在Android中有三种方法：SurfaceView、ImageView、自定义View。

1、使用SurfaceView画一张图：

package com.example.tongjiangsong.surfaceviewdemo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class CommonSurfaceView extends SurfaceView implements SurfaceHolder.Callback,Runnable {

    private SurfaceHolder mHolder;
    private Canvas mCanvas;
    private Path mPath;
    private Paint mPaint;
    //用于绘制的线程
    private Thread mThread;
    //线程状态的标记(线程的控制开关)
    private boolean isRunning;
    private int drawX;
    private int drawY;

    public CommonSurfaceView(Context context) {
        this(context,null);
    }

    public CommonSurfaceView(Context context, AttributeSet attrs) {
        this(context, attrs,0);
    }

    public CommonSurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        //初始化
        mHolder = getHolder();
        mHolder.addCallback(this);//管理生命周期
        mPath=new Path();
        //初始化画笔
        mPaint=new Paint();
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(6);
        mPaint.setAntiAlias(true);
        mPaint.setColor(Color.RED);
        setFocusable(true);
        setFocusableInTouchMode(true);
        this.setKeepScreenOn(true);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {

        isRunning = true;
        mThread = new Thread(this);
        mThread.start();//开启线程
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        isRunning = false;
    }

    /***
     * 注意这个是在子线程中绘制的
     */
    @Override
    public void run() {
        while (isRunning) {
            drawX++;
            drawY = (int) (100 * Math.sin(drawX * 2 * Math.PI / 180) + 400);
            mPath.lineTo(drawX, drawY);
            draw();
        }

    }

    /***
     * 注意这个是在子线程中绘制的，surface支持子线程更新ui，所以
     */
    private void draw() {
        Canvas canvas = null;
        //给画布加锁，防止线程安全，防止该内存区域被其他线程公用
        canvas = mHolder.lockCanvas();
        if (null != canvas) {
            //清屏操作或者设置背景
            canvas.drawColor(Color.WHITE);
            canvas.drawPath(mPath, mPaint);
            //提交显示视图并解锁，防止长期占用此内存
            mHolder.unlockCanvasAndPost(canvas);
        }
    }


}

运行截图：

2、自定义view绘制一张图

package com.example.tongjiangsong.viewdemo;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

import java.util.Random;

public class BallView extends View {
    private Context mContext;
    private AttributeSet mAttrs;
    private Paint paint;        //定义画笔

    public BallView(Context context) {
        super(context);
        this.mContext = context;
        //初始化画笔
        initPaint();
    }
    public BallView(Context context, AttributeSet attrs) {
        super(context, attrs);
        this.mContext = context;
        this.mAttrs = attrs;
        initPaint();
    }
    public BallView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        this.mContext = context;
        this.mAttrs = attrs;
        initPaint();
    }
    private void initPaint(){
        paint = new Paint();
    }

    //重写onDraw方法实现绘图操作
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        paint.setAntiAlias(false);                       //设置画笔为无锯齿
        paint.setColor(Color.BLACK);                    //设置画笔颜色
        canvas.drawColor(Color.WHITE);                  //白色背景
        paint.setStrokeWidth((float) 3.0);              //线宽
        paint.setStyle(Paint.Style.STROKE);                   //空心效果
        canvas.drawCircle(50, 50, 10, paint);           //绘制圆形
        canvas.drawCircle(100, 100, 20, paint);         //绘制圆形
        canvas.drawCircle(150, 150, 30, paint);         //绘制圆形
        canvas.drawCircle(200, 200, 40, paint);         //绘制圆形
        canvas.drawCircle(250, 250, 50, paint);         //绘制圆形
        canvas.drawCircle(300, 300, 60, paint);         //绘制圆形
        canvas.drawCircle(350, 350, 70, paint);         //绘制圆形
    }
}

运行截图：

参考文献：https://blog.csdn.net/ch97ckd/article/details/81740921

https://www.cnblogs.com/JczmDeveloper/p/3873043.html