在Android开发中通过使用View实现进度条功能

在Android开发中通过使用View实现进度条功能？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。

ProgressBarView1（支持拖动）：

ProgressBarView2（不同进度值显示不同颜色，不支持拖拽）：

代码不多，注释也比较详细，全部贴上了：

（一）ProgressBarView1:

public class ProgressBarView1 extends View {    private static final int ARC_FULL_DEGREE = 300;    private int STROKE_WIDTH;    private int width, height;    private float max, progress;    private boolean draggingEnabled = false;    private RectF circleRectF;    private Paint progressPaint;    private Paint textPaint;    private Paint thumbPaint;    private int circleRadius;    private int centerX, centerY;  public ProgressBarView1(Context context) {    super(context);    init();  }  public ProgressBarView1(Context context, AttributeSet attrs) {    super(context, attrs);    init();  }  public ProgressBarView1(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);    init();  }  private void init() {    progressPaint = new Paint();    progressPaint.setAntiAlias(true);    textPaint = new Paint();    textPaint.setColor(Color.WHITE);    textPaint.setAntiAlias(true);    thumbPaint = new Paint();    thumbPaint.setAntiAlias(true);    //使用自定义字体    textPaint.setTypeface(Typeface.createFromAsset(getContext().getAssets(), "fangz.ttf"));  }  @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);    if (width == 0 || height == 0) {      width = getWidth();      height = getHeight();      //计算圆弧半径和圆心点      circleRadius = Math.min(width, height) / 2;      STROKE_WIDTH = circleRadius / 12;      circleRadius -= STROKE_WIDTH;      centerX = width / 2;      centerY = height / 2;      //圆弧所在矩形区域      circleRectF = new RectF();      circleRectF.left = centerX - circleRadius;      circleRectF.top = centerY - circleRadius;      circleRectF.right = centerX + circleRadius;      circleRectF.bottom = centerY + circleRadius;    }  }  private Rect textBounds = new Rect();  @Override  protected void onDraw(canvas canvas) {    super.onDraw(canvas);    float start = 90 + ((360 - ARC_FULL_DEGREE) >> 1); //进度条起始点    float sweep1 = ARC_FULL_DEGREE * (progress / max); //进度划过的角度    float sweep2 = ARC_FULL_DEGREE - sweep1; //剩余的角度    //绘制起始位置小圆形    progressPaint.setColor(Color.WHITE);    progressPaint.setStrokeWidth(0);    progressPaint.setStyle(Paint.Style.FILL);    float radians = (float) (((360.0f - ARC_FULL_DEGREE) / 2) / 180 * Math.PI);    float startX = centerX - circleRadius * (float) Math.sin(radians);    float startY = centerY + circleRadius * (float) Math.cos(radians);    canvas.drawCircle(startX, startY, STROKE_WIDTH / 2, progressPaint);    //绘制进度条    progressPaint.setStrokeWidth(STROKE_WIDTH);    progressPaint.setStyle(Paint.Style.STROKE);//设置空心    canvas.drawArc(circleRectF, start, sweep1, false, progressPaint);    //绘制进度条背景    progressPaint.setColor(Color.parseColor("#d64444"));    canvas.drawArc(circleRectF, start + sweep1, sweep2, false, progressPaint);    //绘制结束位置小圆形    progressPaint.setStrokeWidth(0);    progressPaint.setStyle(Paint.Style.FILL);    float endX = centerX + circleRadius * (float) Math.sin(radians);    float endY = centerY + circleRadius * (float) Math.cos(radians);    canvas.drawCircle(endX, endY, STROKE_WIDTH / 2, progressPaint);    //上一行文字    textPaint.setTextSize(circleRadius >> 1);    String text = (int) (100 * progress / max) + "";    float textLen = textPaint.measureText(text);    //计算文字高度    textPaint.getTextBounds("8", 0, 1, textBounds);    float h2 = textBounds.height();    //% 前面的数字水平居中，适当调整    float extra = text.startsWith("1") &#63; -textPaint.measureText("1") / 2 : 0;    canvas.drawText(text, centerX - textLen / 2 + extra, centerY - 30 + h2 / 2, textPaint);    //百分号    textPaint.setTextSize(circleRadius >> 2);    canvas.drawText("%", centerX + textLen / 2 + extra + 5, centerY - 30 + h2 / 2, textPaint);    //下一行文字    textPaint.setTextSize(circleRadius / 5);    text = "可用内存充足";    textLen = textPaint.measureText(text);    textPaint.getTextBounds(text, 0, text.length(), textBounds);    float h3 = textBounds.height();    canvas.drawText(text, centerX - textLen / 2, centerY + h2 / 2 + h3, textPaint);    //绘制进度位置，也可以直接替换成一张图片    float progressRadians = (float) (((360.0f - ARC_FULL_DEGREE) / 2 + sweep1) / 180 * Math.PI);    float thumbX = centerX - circleRadius * (float) Math.sin(progressRadians);    float thumbY = centerY + circleRadius * (float) Math.cos(progressRadians);    thumbPaint.setColor(Color.parseColor("#33D64444"));    canvas.drawCircle(thumbX, thumbY, STROKE_WIDTH * 2.0f, thumbPaint);    thumbPaint.setColor(Color.parseColor("#99d64444"));    canvas.drawCircle(thumbX, thumbY, STROKE_WIDTH * 1.4f, thumbPaint);    thumbPaint.setColor(Color.WHITE);    canvas.drawCircle(thumbX, thumbY, STROKE_WIDTH * 0.8f, thumbPaint);  }  private boolean isDragging = false;  @Override  public boolean onTouchEvent(@NonNull MotionEvent event) {    if (!draggingEnabled) {      return super.onTouchEvent(event);    }    //处理拖动事件    float currentX = event.getX();    float currentY = event.getY();    int action = event.getAction();    switch (action) {      case MotionEvent.ACTION_DOWN:        //判断是否在进度条thumb位置        if (checkOnArc(currentX, currentY)) {          float newProgress = calDegreeByPosition(currentX, currentY) / ARC_FULL_DEGREE * max;          setProgressSync(newProgress);          isDragging = true;        }        break;      case MotionEvent.ACTION_MOVE:        if (isDragging) {          //判断拖动时是否移出去了          if (checkOnArc(currentX, currentY)) {            setProgressSync(calDegreeByPosition(currentX, currentY) / ARC_FULL_DEGREE * max);          } else {            isDragging = false;          }        }        break;      case MotionEvent.ACTION_UP:        isDragging = false;        break;    }    return true;  }  private float calDistance(float x1, float y1, float x2, float y2) {    return (float) Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));  }    private boolean checkOnArc(float currentX, float currentY) {    float distance = calDistance(currentX, currentY, centerX, centerY);    float degree = calDegreeByPosition(currentX, currentY);    return distance > circleRadius - STROKE_WIDTH * 5 && distance < circleRadius + STROKE_WIDTH * 5        && (degree >= -8 && degree <= ARC_FULL_DEGREE + 8);  }    private float calDegreeByPosition(float currentX, float currentY) {    float a1 = (float) (Math.atan(1.0f * (centerX - currentX) / (currentY - centerY)) / Math.PI * 180);    if (currentY < centerY) {      a1 += 180;    } else if (currentY > centerY && currentX > centerX) {      a1 += 360;    }    return a1 - (360 - ARC_FULL_DEGREE) / 2;  }  public void setMax(int max) {    this.max = max;    invalidate();  }  public void setProgress(float progress) {    final float validProgress = checkProgress(progress);    //动画切换进度值    new Thread(new Runnable() {      @Override      public void run() {        float oldProgress = ProgressBarView1.this.progress;        for (int i = 1; i <= 100; i++) {          ProgressBarView1.this.progress = oldProgress + (validProgress - oldProgress) * (1.0f * i / 100);          postInvalidate();          SystemClock.sleep(20);        }      }    }).start();  }  public void setProgressSync(float progress) {    this.progress = checkProgress(progress);    invalidate();  }  //保证progress的值位于[0,max]  private float checkProgress(float progress) {    if (progress < 0) {      return 0;    }    return progress > max &#63; max : progress;  }  public void setDraggingEnabled(boolean draggingEnabled) {    this.draggingEnabled = draggingEnabled;  }}