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我喜欢制作一个应用程序，有点像小油漆，我必须得到一个位图，在画布上绘制它，然后在它上面绘制（用figer）......所以，我实际上有这个代码：

import java.io.File;
import java.io.FileOutputStream;
import java.util.ArrayList;

import android.content.Context;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Environment;
import android.util.Log;
import android.graphics.Bitmap;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class DrawView extends View implements OnTouchListener {

    private Canvas mCanvas;
    private Path mPath;
    public Paint mPaint;
    private ArrayList<Path> paths = new ArrayList<Path>();
    private boolean start = true;

    public DrawView(Context context) {
    super(context);
    setFocusable(true);
    setFocusableInTouchMode(true);
    this.setOnTouchListener((OnTouchListener) this);
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.BLACK);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(4);
    mPaint.setDither(true);
    mPaint.setFilterBitmap(true);
    mCanvas = new Canvas();
    mPath = new Path();
    paths.add(mPath);
}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
}

@Override
protected void onDraw(Canvas canvas) {

    for (Path p : paths) {
        canvas.drawPath(p, mPaint);

    }
    if (start) {
        Bitmap bmp = BitmapFactory.decodeResource(getResources(),
                R.drawable.v01);
        canvas.drawBitmap(bmp, 0, 0, mPaint);
        start = false;
    }
}

private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;

private void touch_start(float x, float y) {
    mPath.reset();
    mPath.moveTo(x, y);
    mX = x;
    mY = y;
}

private void touch_move(float x, float y) {
    float dx = Math.abs(x - mX);
    float dy = Math.abs(y - mY);
    if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
        mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
        mX = x;
        mY = y;
    }
}

private void touch_up() {
    mPath.lineTo(mX, mY);
    // commit the path to our offscreen
    mCanvas.drawPath(mPath, mPaint);
    // kill this so we don't double draw
    mPath = new Path();
    paths.add(mPath);
}

public boolean onTouch(View arg0, MotionEvent event) {
    float x = event.getX();
    float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        touch_start(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_MOVE:
        touch_move(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_UP:
        touch_up();
        invalidate();
        break;
    }
    return true;
}
}

使用此代码，我可以在画布上绘制，并通过第一种方式获取位图......但是，如果我触摸，位图消失，这就是我根据路径再次绘制的每个 onTouch 事件的原因......我怎么能做我喜欢的事？，我的意思是，获取位图，然后在它上面绘制...

4

4 回答 4

0

这将使您的视图非常缓慢，但是如果您删除该if(start)语句，那么您的位图将不会消失。

更好canvas.drawBitmap()的方法是采用外部if(start)方法，但这仍然会很慢，因为每次触摸屏幕时都会绘制位图。

实际上，这是因为每次onDraw()调用时都会传递一个空白位图。这意味着您必须在每次调用 onDraw 时重新绘制所有内容，但是因为您只是第一次设置位图，所以当再次调用 on draw 时，位图不会再次添加，因此消失。

于 2013-06-11T19:26:59.070 回答
0

如果将 canvas.drawBitmap() 移到 if 语句之外，应该可以工作。将解码保留在那里，但将实际绘图移出它。

于 2013-06-07T17:37:21.077 回答
0

我不确定你的问题是什么。每次运行时都必须重新绘制位图onDraw，否则那里什么也没有。你真的注意到那里有任何性能损失吗？

您不必做的是解码每个invalidate.

将您的 bmp 声明为全局变量

Bitmap bmp;

将位图存储在构造函数中：

DrawView(Context context){
  ...
  bmp = BitmapFactory.decodeResource(getResources(),
                    R.drawable.v01);
  }

并删除您的 draw 方法上的 if 。你不想要 if 那里。每次调用 invalidate 时都必须重新绘制位图。但这不应该导致任何性能问题。

canvas.drawBitmap(bmp, 0, 0, mPaint);
于 2013-06-11T16:19:55.543 回答
0

已解决，我使用此代码可以加载图像并在其上绘制...

DrawView.java

package com.example.com.dibuja;

import java.util.ArrayList;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

public class DrawView extends View implements OnTouchListener {
private Canvas mCanvas;
private Path mPath;
public Paint mPaint;
private ArrayList<Path> paths = new ArrayList<Path>();
Bitmap bmp;

public DrawView(Context context) {
    super(context);
    setFocusable(true);
    setFocusableInTouchMode(true);

    this.setOnTouchListener(this);
    bmp = BitmapFactory.decodeResource(getResources(), R.drawable.v01);
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.BLUE);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(6);
    mCanvas = new Canvas();
    mPath = new Path();
    paths.add(mPath);

}

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawBitmap(bmp, 0, 0, mPaint);
    for (Path p : paths) {
        canvas.drawPath(p, mPaint);
    }
}

private float mX, mY;
private static final float TOUCH_TOLERANCE = 0;
Draw dw = new Draw();

private void touch_start(float x, float y) {
    mPath.reset();
    mPath.moveTo(x, y);
    mX = x;
    mY = y;

}

private void touch_move(float x, float y) {
    float dx = Math.abs(x - mX);
    float dy = Math.abs(y - mY);
    if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
        mPath.quadTo(mX, mY, (x + mX) / 2, (y + mY) / 2);
        mX = x;
        mY = y;
    }

}

private void touch_up() {
    mPath.lineTo(mX, mY);
    // commit the path to our offscreen
    mCanvas.drawPath(mPath, mPaint);
    // kill this so we don't double draw
    mPath = new Path();
    paths.add(mPath);
}

@Override
public boolean onTouch(View arg0, MotionEvent event) {
    float x = event.getX();
    float y = event.getY();

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        touch_start(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_MOVE:
        touch_move(x, y);
        invalidate();
        break;
    case MotionEvent.ACTION_UP:
        touch_up();
        invalidate();
        break;
    }
    return true;
}
}
于 2013-07-23T17:22:18.097 回答