画布没有正确绘制我的缩放文本

Question

我看到只有0写的比例！如同图片和模式中的两个奇怪的零:( GALAXY NEXUS 4.2.1）

与http://mindtherobot.com/blog/272/android-custom-ui-making-a-vintage-thermometer/comment-page-1/#comment-106122%29中的示例一样，这是我的自定义视图：

package com.wikibuyers.barometro;
import java.util.List;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapShader;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.LightingColorFilter;
import android.graphics.LinearGradient;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RadialGradient;
import android.graphics.RectF;
import android.graphics.Shader;
import android.graphics.Typeface;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Handler;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;



public class Barometro extends View implements SensorEventListener{

private static final String TAG = Barometro.class.getSimpleName();

private Handler handler;

// drawing tools
    private RectF rimRect;
    private Paint rimPaint;
    private Paint rimCirclePaint;

    private RectF faceRect;
    private Bitmap faceTexture;
    private Paint facePaint;
    private Paint rimShadowPaint;

    private Paint scalePaint;
    private RectF scaleRect;

    private Paint titlePaint;   
    private Path titlePath;

    private Paint logoPaint;
    private Bitmap logo;
    private Matrix logoMatrix;
    private float logoScale;

    private Paint handPaint;
    private Path handPath;
    private Paint handScrewPaint;

    private Paint backgroundPaint; 
    // end drawing tools

    private Bitmap background; // holds the cached static part

    // scale configuration
    private static final int totalNicks = 100;
    private static final float degreesPerNick = 360.0f / totalNicks;    
    private static final int centerDegree = 40; // the one in the top center (12 o'clock)
    private static final int minDegrees = -30;
    private static final int maxDegrees = 110;

    // hand dynamics -- all are angular expressed in F degrees
    private boolean handInitialized = false;
    private float handPosition = centerDegree;
    private float handTarget = centerDegree;
    private float handVelocity = 0.0f;
    private float handAcceleration = 0.0f;
    private long lastHandMoveTime = -1L;



    public Barometro(Context context) {
        super(context);
        init();
    }

    public Barometro(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public Barometro(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        init();
    }


    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        attachToSensor();
    }

    @Override
    protected void onDetachedFromWindow() {
        detachFromSensor();
        super.onDetachedFromWindow();
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {
        Bundle bundle = (Bundle) state;
        Parcelable superState = bundle.getParcelable("superState");
        super.onRestoreInstanceState(superState);

        handInitialized = bundle.getBoolean("handInitialized");
        handPosition = bundle.getFloat("handPosition");
        handTarget = bundle.getFloat("handTarget");
        handVelocity = bundle.getFloat("handVelocity");
        handAcceleration = bundle.getFloat("handAcceleration");
        lastHandMoveTime = bundle.getLong("lastHandMoveTime");
    }

    @Override
    protected Parcelable onSaveInstanceState() {
        Parcelable superState = super.onSaveInstanceState();

        Bundle state = new Bundle();
        state.putParcelable("superState", superState);
        state.putBoolean("handInitialized", handInitialized);
        state.putFloat("handPosition", handPosition);
        state.putFloat("handTarget", handTarget);
        state.putFloat("handVelocity", handVelocity);
        state.putFloat("handAcceleration", handAcceleration);
        state.putLong("lastHandMoveTime", lastHandMoveTime);
        return state;
    }

    @SuppressLint({ "NewApi", "InlinedApi" })
    private void init() {
        handler = new Handler();

        setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        initDrawingTools();
    }

    private String getTitle() {
        return "wikibuyers.com";
    }

    private SensorManager getSensorManager() {
        return (SensorManager) getContext().getSystemService(Context.SENSOR_SERVICE);       
    }

    private void attachToSensor() {
        SensorManager sensorManager = getSensorManager();

        List<Sensor> sensors = sensorManager.getSensorList(Sensor.TYPE_PRESSURE);
        if (sensors.size() > 0) {
            Sensor sensor = sensors.get(0);
            sensorManager.registerListener(this, sensor, SensorManager.SENSOR_DELAY_NORMAL, handler);
        } else {
            Log.e(TAG, "No pressure sensor found");
        }       
    }

    private void detachFromSensor() {
        SensorManager sensorManager = getSensorManager();
        sensorManager.unregisterListener(this);
    }

    private void initDrawingTools() {
        rimRect = new RectF(0.1f, 0.1f, 0.9f, 0.9f);

        // the linear gradient is a bit skewed for realism
        rimPaint = new Paint();
        rimPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
        rimPaint.setShader(new LinearGradient(0.40f, 0.0f, 0.60f, 1.0f, 
                                           Color.rgb(0xf0, 0xf5, 0xf0),
                                           Color.rgb(0x30, 0x31, 0x30),
                                           Shader.TileMode.CLAMP));     

        rimCirclePaint = new Paint();
        rimCirclePaint.setAntiAlias(true);
        rimCirclePaint.setStyle(Paint.Style.STROKE);
        rimCirclePaint.setColor(Color.argb(0x4f, 0x33, 0x36, 0x33));
        rimCirclePaint.setStrokeWidth(0.005f);

        float rimSize = 0.02f;
        faceRect = new RectF();
        faceRect.set(rimRect.left + rimSize, rimRect.top + rimSize, 
                 rimRect.right - rimSize, rimRect.bottom - rimSize);        

        faceTexture = BitmapFactory.decodeResource(getContext().getResources(), 
                   R.drawable.plastic);
        BitmapShader paperShader = new BitmapShader(faceTexture, 
                                                    Shader.TileMode.MIRROR, 
                                                    Shader.TileMode.MIRROR);
        Matrix paperMatrix = new Matrix();
        facePaint = new Paint();
        facePaint.setFilterBitmap(true);
        paperMatrix.setScale(1.0f / faceTexture.getWidth(), 
                             1.0f / faceTexture.getHeight());
        paperShader.setLocalMatrix(paperMatrix);
        facePaint.setStyle(Paint.Style.FILL);
        facePaint.setShader(paperShader);

        rimShadowPaint = new Paint();
        rimShadowPaint.setShader(new RadialGradient(0.5f, 0.5f, faceRect.width() / 2.0f, 
                   new int[] { 0x00000000, 0x00000500, 0x50000500 },
                   new float[] { 0.96f, 0.96f, 0.99f },
                   Shader.TileMode.MIRROR));
        rimShadowPaint.setStyle(Paint.Style.FILL);

        scalePaint = new Paint();
        scalePaint.setStyle(Paint.Style.STROKE);
        scalePaint.setColor(0x9f004d0f);
        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);        

        float scalePosition = 0.10f;
        scaleRect = new RectF();
        scaleRect.set(faceRect.left + scalePosition, faceRect.top + scalePosition,
                      faceRect.right - scalePosition, faceRect.bottom - scalePosition);

        titlePaint = new Paint();
        titlePaint.setColor(0xaf946109);
        titlePaint.setAntiAlias(true);
        titlePaint.setTypeface(Typeface.DEFAULT_BOLD);
        titlePaint.setTextAlign(Paint.Align.CENTER);
        titlePaint.setTextSize(0.05f);
        titlePaint.setTextScaleX(0.8f);

        titlePath = new Path();
        titlePath.addArc(new RectF(0.24f, 0.24f, 0.76f, 0.76f), -180.0f, -180.0f);

        logoPaint = new Paint();
        logoPaint.setFilterBitmap(true);
        logo = BitmapFactory.decodeResource(getContext().getResources(), R.drawable.logo);
        logoMatrix = new Matrix();
        logoScale = (1.0f / logo.getWidth()) * 0.3f;;
        logoMatrix.setScale(logoScale, logoScale);

        handPaint = new Paint();
        handPaint.setAntiAlias(true);
        handPaint.setColor(0xff392f2c);     
        handPaint.setShadowLayer(0.01f, -0.005f, -0.005f, 0x7f000000);
        handPaint.setStyle(Paint.Style.FILL);   

        handPath = new Path();
        handPath.moveTo(0.5f, 0.5f + 0.2f);
        handPath.lineTo(0.5f - 0.010f, 0.5f + 0.2f - 0.007f);
        handPath.lineTo(0.5f - 0.002f, 0.5f - 0.32f);
        handPath.lineTo(0.5f + 0.002f, 0.5f - 0.32f);
        handPath.lineTo(0.5f + 0.010f, 0.5f + 0.2f - 0.007f);
        handPath.lineTo(0.5f, 0.5f + 0.2f);
        handPath.addCircle(0.5f, 0.5f, 0.025f, Path.Direction.CW);

        handScrewPaint = new Paint();
        handScrewPaint.setAntiAlias(true);
        handScrewPaint.setColor(0xff493f3c);
        handScrewPaint.setStyle(Paint.Style.FILL);

        backgroundPaint = new Paint();
        backgroundPaint.setFilterBitmap(true);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        Log.d(TAG, "Width spec: " + MeasureSpec.toString(widthMeasureSpec));
        Log.d(TAG, "Height spec: " + MeasureSpec.toString(heightMeasureSpec));

        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);

        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);

        int chosenWidth = chooseDimension(widthMode, widthSize);
        int chosenHeight = chooseDimension(heightMode, heightSize);

        int chosenDimension = Math.min(chosenWidth, chosenHeight);

        setMeasuredDimension(chosenDimension, chosenDimension);
    }

    private int chooseDimension(int mode, int size) {
        if (mode == MeasureSpec.AT_MOST || mode == MeasureSpec.EXACTLY) {
            return size;
        } else { // (mode == MeasureSpec.UNSPECIFIED)
            return getPreferredSize();
        } 
    }

    // in case there is no size specified
    private int getPreferredSize() {
        return 300;
    }

    private void drawRim(Canvas canvas) {
        // first, draw the metallic body
        canvas.drawOval(rimRect, rimPaint);
        // now the outer rim circle
        canvas.drawOval(rimRect, rimCirclePaint);
    }

    private void drawFace(Canvas canvas) {      
        canvas.drawOval(faceRect, facePaint);
        // draw the inner rim circle
        canvas.drawOval(faceRect, rimCirclePaint);
        // draw the rim shadow inside the face
        canvas.drawOval(faceRect, rimShadowPaint);
    }

    private void drawScale(Canvas canvas) {
        canvas.drawOval(scaleRect, scalePaint);

        canvas.save(Canvas.MATRIX_SAVE_FLAG);
        for (int i = 0; i < totalNicks; ++i) {
            float y1 = scaleRect.top;
            float y2 = y1 - 0.020f;

            canvas.drawLine(0.5f, y1, 0.5f, y2, scalePaint);



            if ((i % 5) == 0) {
                int value = nickToDegree(i);

                if ((value >= minDegrees) && (value <= maxDegrees)) {
                    String valueString = Integer.toString(value);
                    canvas.drawText(valueString, 0.5f, y2 - 0.015f, scalePaint);

                }
            }

            canvas.rotate(degreesPerNick, 0.5f, 0.5f);


        }
        canvas.restore();

    }

    private int nickToDegree(int nick) {
        int rawDegree = ((nick < totalNicks / 2) ? nick : (nick - totalNicks)) * 2;
        int shiftedDegree = rawDegree + centerDegree;
        return shiftedDegree;
    }

    private float degreeToAngle(float degree) {
        return (degree - centerDegree) / 2.0f * degreesPerNick;
    }

    private void drawTitle(Canvas canvas) {
        String title = getTitle();
        canvas.drawTextOnPath(title, titlePath, 0.0f,0.0f, titlePaint);             
    }

    private void drawLogo(Canvas canvas) {
        canvas.save(Canvas.MATRIX_SAVE_FLAG);
        canvas.translate(0.5f - logo.getWidth() * logoScale / 2.0f, 
                         0.5f - logo.getHeight() * logoScale / 2.0f);

        int color = 0x00000000;
        float position = getRelativePressurePosition();
        if (position < 0) {
            color |= (int) ((0xf0) * -position); // blue
        } else {
            color |= ((int) ((0xf0) * position)) << 16; // red          
        }
        //Log.d(TAG, "*** " + Integer.toHexString(color));
        LightingColorFilter logoFilter = new LightingColorFilter(0xff338822, color);
        logoPaint.setColorFilter(logoFilter);

        canvas.drawBitmap(logo, logoMatrix, logoPaint);
        canvas.restore();       
    }

    private void drawHand(Canvas canvas) {
        if (handInitialized) {
            float handAngle = degreeToAngle(handPosition);
            canvas.save(Canvas.MATRIX_SAVE_FLAG);
            canvas.rotate(handAngle, 0.5f, 0.5f);
            canvas.drawPath(handPath, handPaint);
            canvas.restore();

            canvas.drawCircle(0.5f, 0.5f, 0.01f, handScrewPaint);
        }
    }

    private void drawBackground(Canvas canvas) {
        if (background == null) {
            Log.w(TAG, "Background not created");
        } else {
            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);

        drawLogo(canvas);
        drawHand(canvas);

        canvas.restore();

        if (handNeedsToMove()) {
            moveHand();
        }
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        Log.d(TAG, "Size changed to " + w + "x" + h);

        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);

        drawRim(backgroundCanvas);
        drawFace(backgroundCanvas);
        drawScale(backgroundCanvas);
        drawTitle(backgroundCanvas);        
    }

    private boolean handNeedsToMove() {
        return Math.abs(handPosition - handTarget) > 0.001f;
    }

    private void moveHand() {
        if (! handNeedsToMove()) {
            return;
        }

        if (lastHandMoveTime != -1L) {
            long currentTime = System.currentTimeMillis();
            float delta = (currentTime - lastHandMoveTime) / 1000.0f;

            float direction = Math.signum(handVelocity);
            if (Math.abs(handVelocity) < 90.0f) {
                handAcceleration = 5.0f * (handTarget - handPosition);
            } else {
                handAcceleration = 0.0f;
            }
            handPosition += handVelocity * delta;
            handVelocity += handAcceleration * delta;
            if ((handTarget - handPosition) * direction < 0.01f * direction) {
                handPosition = handTarget;
                handVelocity = 0.0f;
                handAcceleration = 0.0f;
                lastHandMoveTime = -1L;
            } else {
                lastHandMoveTime = System.currentTimeMillis();              
            }
            invalidate();
        } else {
            lastHandMoveTime = System.currentTimeMillis();
            moveHand();
        }
    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {

    }

    @Override
    public void onSensorChanged(SensorEvent sensorEvent) {
        if (sensorEvent.values.length > 0) {
            float pressureAtm = sensorEvent.values[0]/20;
            //Log.i(TAG, "*** Temperature: " + temperatureC);

            float pressureMmg = (9.0f / 5.0f) * pressureAtm + 32.0f;
            setHandTarget(pressureAtm);
        } else {
            Log.w(TAG, "Empty sensor event received");
        }
    }

    private float getRelativePressurePosition() {
        if (handPosition < centerDegree) {
            return - (centerDegree - handPosition) / (float) (centerDegree - minDegrees);
        } else {
            return (handPosition - centerDegree) / (float) (maxDegrees - centerDegree);
        }
    }

    private void setHandTarget(float pressure) {
        if (pressure < minDegrees) {
            pressure = minDegrees;
        } else if (pressure > maxDegrees) {
            pressure = maxDegrees;
        }
        handTarget = pressure;
        handInitialized = true;
        invalidate();
    }

}

重点关注drawScale（）方法：

private void drawScale(Canvas canvas) {
        canvas.drawOval(scaleRect, scalePaint);

        canvas.save(Canvas.MATRIX_SAVE_FLAG);
        for (int i = 0; i < totalNicks; ++i) {
            float y1 = scaleRect.top;
            float y2 = y1 - 0.020f;

            canvas.drawLine(0.5f, y1, 0.5f, y2, scalePaint);



            if ((i % 5) == 0) {
                int value = nickToDegree(i);

                if ((value >= minDegrees) && (value <= maxDegrees)) {
                    String valueString = Integer.toString(value);
                    canvas.drawText(valueString, 0.5f, y2 - 0.015f, scalePaint);

                }
            }

            canvas.rotate(degreesPerNick, 0.5f, 0.5f);


        }
        canvas.restore();

    }