我碰到了一堵墙，这个基本的drawRect没有显示任何东西，我无法弄清楚原因。
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
canvas.drawCircle(circle1x, circle1y, circleRadius, circlePaint);
canvas.drawCircle(circle2x, circle2y, circleRadius, circlePaint);
canvas.drawRect(rect, rectPaint);
}
在onDraw之前运行，并从View构造函数调用以设置所有var
private void setupCropping() {
final float scale = getContext().getResources().getDisplayMetrics().density;
circleRadius = (int) (circleRadiusDp * scale + 0.5f);
DisplayMetrics metrics = new DisplayMetrics();
((Activity) getContext()).getWindowManager().getDefaultDisplay().getMetrics(metrics);
displayX = metrics.widthPixels;
displayY = metrics.heightPixels;
cropAreaY = displayY / 3;
cropAreaX = displayX;
//Setting up the circles for adjusting
circle1x = displayX / 2;
circle1y = displayY / 2 - (cropAreaY / 2);
circle2x = displayX / 2;
circle2y = displayY / 2 + (cropAreaY / 2);
canvasPaint = new Paint();
canvasPaint.setColor(0xffffff00);
circlePaint = new Paint();
circlePaint.setColor(0xffffff00);
circlePaint.setAntiAlias(true);
rectPaint = new Paint();
rectPaint.setColor(0xffffff00);
rect = new Rect();
rect.set(0, circle1y, 0, displayY - cropAreaY - circle1y);
}
drawCircle工作得非常完美，并且正如我所期待的那样，我已经检查了drawRect给出的数字，并且它们被设置为应该如此，所以我真的不知道可能是什么这里出错了。
package com.samplersnapshoot.domiq.samplersnapshoot;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.View;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.util.concurrent.CountDownLatch;
/**
* Created by domix on 14.8.2015..
*/
public class CroppingView extends View {
public final String TAG = "DEBUG";
private Canvas cropCanvas;
private Bitmap canvasBitmap;
private int displayX;
private int displayY;
private int circle1x = 0;
private int circle2x = 0;
private int circle1y = 0;
private int circle2y = 0;
private int circleRadiusDp = 20;
private int circleRadius = 100;
private int cropAreaX = 0;
private int cropAreaY = 0;
private Rect rect;
private Paint canvasPaint;
private Paint circlePaint;
private Paint rectPaint;
public CroppingView(Context context, AttributeSet attrs){
super(context, attrs);
setupCropping();
}
private void setupCropping() {
final float scale = getContext().getResources().getDisplayMetrics().density;
circleRadius = (int) (circleRadiusDp * scale + 0.5f);
DisplayMetrics metrics = new DisplayMetrics();
((Activity) getContext()).getWindowManager().getDefaultDisplay().getMetrics(metrics);
displayX = metrics.widthPixels;
displayY = metrics.heightPixels;
cropAreaY = displayY / 3;
cropAreaX = displayX;
//Setting up the circles for adjusting
circle1x = displayX / 2;
circle1y = displayY / 2 - (cropAreaY / 2);
circle2x = displayX / 2;
circle2y = displayY / 2 + (cropAreaY / 2);
canvasPaint = new Paint();
canvasPaint.setColor(0xffffff00);
circlePaint = new Paint();
circlePaint.setColor(0xffffff00);
circlePaint.setAntiAlias(true);
rectPaint = new Paint();
rectPaint.setARGB(50, 135, 225, 255);
}
/*@Override
protected void onMeasure (int widthMeasureSpec, int heightMeasureSpec) {
displayX = widthMeasureSpec;
displayY = heightMeasureSpec;
invalidate();
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}*/
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
//Getting bitmap
getPath myPath = new getPath();
final File myFile = myPath.getLastModifiedFile();
final CountDownLatch latch = new CountDownLatch(1);
Thread getCanvasBitmap = new Thread() {
public void run() {
BitmapFactory.Options opt = new BitmapFactory.Options();
opt.inDither = true;
opt.inPreferredConfig = Bitmap.Config.ARGB_8888;
int i = 0;
while (canvasBitmap == null && ++i < 500) {
System.gc();
Log.d(TAG, "Trying again: " + i);
canvasBitmap = BitmapFactory.decodeFile(myFile.getAbsolutePath(), opt);
}
latch.countDown();
}
};
getCanvasBitmap.start();
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
//Turning into mutable bitmap
myFile.getParentFile().mkdirs();
RandomAccessFile randomAccessFile = null;
try {
randomAccessFile = new RandomAccessFile(myFile, "rw");
} catch (FileNotFoundException e) {
e.printStackTrace();
}
int bWidth = canvasBitmap.getWidth();
int bHeight = canvasBitmap.getHeight();
FileChannel channel = randomAccessFile.getChannel();
MappedByteBuffer map = null;
try {
map = channel.map(FileChannel.MapMode.READ_WRITE, 0, bWidth*bHeight*4);
} catch (IOException e) {
e.printStackTrace();
}
canvasBitmap.copyPixelsToBuffer(map);
canvasBitmap.recycle();
this.canvasBitmap = Bitmap.createBitmap(bWidth, bHeight, Bitmap.Config.ARGB_8888);
map.position(0);
this.canvasBitmap.copyPixelsFromBuffer(map);
try {
channel.close();
} catch (IOException e) {
e.printStackTrace();
}
try {
randomAccessFile.close();
} catch (IOException e) {
e.printStackTrace();
}
}
protected void onDraw(Canvas canvas) {
canvas.drawBitmap(canvasBitmap, 0, 0, canvasPaint);
Log.d(TAG, "Display vars:" + displayX + " " + displayY);
canvas.drawCircle(circle1x, circle1y, circleRadius, circlePaint);
canvas.drawCircle(circle2x, circle2y, circleRadius, circlePaint);
rect = new Rect();
rect.set(5, circle1y, displayX, displayY - cropAreaY - circle1y);
canvas.drawRect(rect, rectPaint);
}
}
这个类远没有很好的编码，我还没有整合很多功能并清理它。
答案 0 :(得分：4)
rect.set(0, circle1y, 0, displayY - cropAreaY - circle1y);
您的left和right坐标都是0.去图。
这是
rect.set(int left, int top, int right, int bottom);
编辑：
好的，我设法找出问题所在。以下行位于View类
rect.set(5, circle1y, displayX, displayY - cropAreaY - circle1y);
在代码中使用相同的计算，对于具有480x800显示器的设备，我得到以下坐标值。
rect.set(5, 267, 480, 267);
同样，您Rect的重叠边重叠;您的top和bottom边都在同一个Y坐标上。这将生成262像素宽且零高度的矩形。
您需要做的就是更新坐标计算并提供正确的坐标。否则，你的Rect应该画得很好。