SurfaceView

Android View之SurfaceView优点

2018-04-26  本文已影响315人  Jowney

View更新UI问题

对于一个View的onDraw方法，不能这样做，因为从后台线程修改一个GUI元素会被显式地禁止的。
当需要快速地更新View的UI，或者当渲染代码阻塞GUI线程的时间过长的时候，SurfaceView就是解决上述问题的最佳选择。

SurfaceView和View的区别

SurfaceView原理

创建SurfaceView

使用场景

简单画图板代码

package com.hcsys.display.views;

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.util.EventLog;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

/**
 * des:
 * author: admin
 * time: 2016/10/24 11:32.
 * e-mail：guohaichang@163.com
 */
public class CustomSurfaceView extends SurfaceView implements SurfaceHolder.Callback, Runnable {
    // SurfaceHolder
    private SurfaceHolder mHolder;
    // 用于绘图的Canvas
    private Canvas mCanvas;
    // 子线程标志位
    private volatile boolean mIsDrawing;
    //画笔
    private Paint mPaint;
    //绘制路径
    private Path mPath;

    public CustomSurfaceView(Context context) {
        super(context);
        initView();
    }

    public CustomSurfaceView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView();
    }

    public CustomSurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        initView();
    }

    private void initView() {
        mHolder = getHolder();
        mHolder.addCallback(this);
        setFocusable(true);
        setFocusableInTouchMode(true);
        this.setKeepScreenOn(true);
        //mHolder.setFormat(PixelFormat.OPAQUE);
        mPaint = new Paint();
        mPaint.setColor(Color.BLUE);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(10);
        mPaint.setAntiAlias(true);//抗锯齿
        mPath = new Path();
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mIsDrawing = true;
        new Thread(this).start();
    }

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

    }

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

    @Override
    public void run() {
        long start = System.currentTimeMillis();
        while (mIsDrawing) {
            draw();
        }
        long end = System.currentTimeMillis();
        // 50 - 100
        if (end - start < 100) {//保证线程运行时间不少于100ms
            try {
                Thread.sleep(100 - (end - start));
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    private synchronized void draw() {
        try {
            mCanvas = mHolder.lockCanvas();
            mCanvas.drawColor(Color.WHITE);
            mCanvas.drawPath(mPath,mPaint);
        } catch (Exception e) {
        } finally {
            if (mCanvas != null){
                mHolder.unlockCanvasAndPost(mCanvas);
            }
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                mPath.moveTo(event.getX(),event.getY());
                break;
            case MotionEvent.ACTION_MOVE:
                mPath.lineTo(event.getX(),event.getY());
                break;
            case MotionEvent.ACTION_UP:

                break;
        }
        return true;
    }
}
上一篇 下一篇

猜你喜欢

热点阅读