第四讲 复杂应用组件 Handler机制、多线程、 自定义View
包含了以下内容
- ppt - 本地课程的讲义
- assignment - 本次课程的作业：绘制一个桌面时钟，在Clock.java类中完成todo部分
private Handler handler = new Handler();
private Runnable runnable = new Runnable() {
@Override
public void run() {
invalidate();
handler.postDelayed(this, 1000); // 每秒刷新一次
}
}; private void init(Context context, AttributeSet attrs) {
this.degreesColor = DEFAULT_PRIMARY_COLOR;
mNeedlePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mNeedlePaint.setStyle(Paint.Style.FILL_AND_STROKE);
mNeedlePaint.setStrokeCap(Paint.Cap.ROUND);
handler.post(runnable); // 启动定时任务
}
private void drawHoursValues(Canvas canvas) {
// Default Color:
// - hoursValuesColor
//有60个刻度，各5个刻一个
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.WHITE);
paint.setTextSize(mWidth * 0.05f); // 设置文本大小
paint.setTextAlign(Paint.Align.CENTER); // 设置文本对齐方式
// 半径设置为比刻度短一些，以便将数字绘制在表盘内侧
int radius = mCenterX - (int) (mWidth * 0.1f);
// 遍历每个小时并绘制
for (int i = 0; i < 12; i++) {
// 计算每个小时的位置，0小时位于正上方
float angle = (float) (i * 30); // 每小时间隔30度
float angleInRadians = (float) Math.toRadians(angle);
// 计算文本的位置
float x = (float) (mCenterX + radius * Math.sin(angleInRadians));
float y = (float) (mCenterY - radius * Math.cos(angleInRadians));
// 绘制小时数字（1-12）
canvas.drawText(String.valueOf(i == 0 ? 12 : i), x, y + paint.getTextSize() / 3, paint);
}
}
private void drawNeedles(final Canvas canvas) {
Calendar calendar = Calendar.getInstance();
Date now = calendar.getTime();
int nowHours = now.getHours();
int nowMinutes = now.getMinutes();
int nowSeconds = now.getSeconds();
// 画秒针
drawPointer(canvas, 2, nowSeconds);
// 画分针
// todo 画分针
drawPointer(canvas, 1, nowMinutes);
// 画时针
int part = nowMinutes / 12;
drawPointer(canvas, 0, 5 * (nowHours+8) + part);
System.out.println("part:"+part+" nowHours:"+nowHours);
}
private void drawPointer(Canvas canvas, int pointerType, int value) {
float degree;
float[] pointerHeadXY = new float[2];
mNeedlePaint.setStrokeWidth(mWidth * DEFAULT_DEGREE_STROKE_WIDTH);
switch (pointerType) {
case 0:
degree = value * UNIT_DEGREE;
mNeedlePaint.setColor(Color.WHITE);
pointerHeadXY = getPointerHeadXY(HOUR_POINTER_LENGTH, degree);
break;
case 1:
// todo 画分针，设置分针的颜色
degree = value * UNIT_DEGREE;
mNeedlePaint.setColor(Color.BLACK);
pointerHeadXY = getPointerHeadXY(MINUTE_POINTER_LENGTH, degree);
break;
case 2:
degree = value * UNIT_DEGREE;
mNeedlePaint.setColor(Color.GREEN);
pointerHeadXY = getPointerHeadXY(SECOND_POINTER_LENGTH, degree);
break;
}
canvas.drawLine(mCenterX, mCenterY, pointerHeadXY[0], pointerHeadXY[1], mNeedlePaint);
}