下面的代码是一个自定义视图 - 它绘制一个圆圈，根据比例添加凹口并添加比例文本。这源自 Mind The Robot 关于创建老式温度计的优秀教程。http://mindtherobot.com/blog/272/android-custom-ui-making-a-vintage-thermometer/
此代码在运行至 Jelly Bean 4.1.2 的设备上运行良好，但在 4.2 上中断。在 4.2 上，数字不再围绕圆圈绘制，但似乎遍布整个屏幕。代码在 Nexus 7 上运行良好，直到它获得 4.2 更新，所以它不可能是设备问题。我已经在运行 4.1.2 的 Nexus S 和运行 4.2 的 Nexus 4 上对其进行了测试，它在 Nexus S 上运行良好，但在 Nexus 4 上运行良好。
不幸的是，作为一个新用户，我无法发布屏幕截图，我将尝试描述它：数字在表盘的前半部分正确显示，其余数字分散在屏幕上。
我查看了 4.2 更改日志，但看不到任何会导致这种情况发生的事情。我在网上寻找过类似的问题，但这些似乎都与硬件加速有关——我尝试了在清单中设置硬件加速的各种组合，但没有任何影响。
我真的很感激任何可能导致这种情况发生的输入。
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Typeface;
import android.util.AttributeSet;
import android.view.View;
public class AneroidView extends View {
// drawing tools
private RectF rimRect;
private RectF faceRect;
private Paint scalePaint;
private RectF scaleRect;
private Paint backgroundPaint;
// end drawing tools
private Bitmap background; // holds the cached static part
private int totalNotches = 130;
private int incrementPerLargeNotch = 10;
private int incrementPerSmallNotch = 1;
private float degreesPerNotch = 360.0f / totalNotches;
private int scaleCenterValue = 1000; // the one in the top center (12 o'clock)
private int scaleMinValue = 935;
private int scaleMaxValue = 1065;
public AneroidView(Context context) {
super(context);
init(context, null);
}
public AneroidView(Context context, AttributeSet attrs) {
super(context, attrs);
init(context, attrs);
}
public AneroidView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
init(context, attrs);
}
private void init(Context context, AttributeSet attrs) {
rimRect = new RectF(0.1f, 0.1f, 0.9f, 0.9f);
float rimSize = 0.02f;
faceRect = new RectF();
faceRect.set(rimRect.left + rimSize, rimRect.top + rimSize,
rimRect.right - rimSize, rimRect.bottom - rimSize);
scalePaint = new Paint();
scalePaint.setStyle(Paint.Style.STROKE);
scalePaint.setColor(Color.rgb(49, 79, 79));
scalePaint.setStrokeWidth(0.005f);
scalePaint.setAntiAlias(true);
scalePaint.setTextSize(0.045f);
scalePaint.setTypeface(Typeface.SANS_SERIF);
scalePaint.setTextScaleX(0.8f);
scalePaint.setTextAlign(Paint.Align.CENTER);
// The scale rectangular is located .10 from the outer rim.
float scalePosition = 0.10f;
scaleRect = new RectF();
scaleRect.set(faceRect.left + scalePosition, faceRect.top + scalePosition,
faceRect.right - scalePosition, faceRect.bottom - scalePosition);
}
private void drawScale(Canvas canvas) {
// Draw a large notch every large increment, and a small
// notch every small increment.
canvas.drawOval(scaleRect, scalePaint);
canvas.save(Canvas.MATRIX_SAVE_FLAG);
for (int i = 0; i < totalNotches; ++i) {
float y1 = scaleRect.top;
float y2 = y1 - 0.015f;
float y3 = y1 - 0.025f;
int value = notchToValue(i);
if (i % (incrementPerLargeNotch/incrementPerSmallNotch) == 0) {
if (value >= scaleMinValue && value <= scaleMaxValue) {
// draw a nick
canvas.drawLine(0.5f, y1, 0.5f, y3, scalePaint);
String valueString = Integer.toString(value);
// Draw the text 0.15 away from y3 which is the long nick.
canvas.drawText(valueString, 0.5f, y3 - 0.015f, scalePaint);
}
}
else{
if (value >= scaleMinValue && value <= scaleMaxValue) {
// draw a nick
canvas.drawLine(0.5f, y1, 0.5f, y2, scalePaint);
}
}
canvas.rotate(degreesPerNotch, 0.5f, 0.5f);
}
canvas.restore();
}
private int notchToValue(int value) {
int rawValue = ((value < totalNotches / 2) ? value : (value - totalNotches)) * incrementPerSmallNotch;
int shiftedValue = rawValue + scaleCenterValue;
return shiftedValue;
}
private void drawBackground(Canvas canvas) {
if (background != null)
canvas.drawBitmap(background, 0, 0, backgroundPaint);
}
@Override
protected void onDraw(Canvas canvas) {
drawBackground(canvas);
float scale = (float) getWidth();
canvas.save(Canvas.MATRIX_SAVE_FLAG);
canvas.scale(scale, scale);
canvas.restore();
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
regenerateBackground();
}
private void regenerateBackground() {
// free the old bitmap
if (background != null) {
background.recycle();
}
background = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
Canvas backgroundCanvas = new Canvas(background);
float scale = (float) getWidth();
backgroundCanvas.scale(scale, scale);
drawScale(backgroundCanvas);
}
}