Android自定义View实例AnalogClock源码

[来源] 达内    [编辑] 达内   [时间]2012-12-05

针对Android底层View的直接构造很多网友没有实战经验,本次Android开发网结合目前平台开源代码一起通过AnalogClock类 来理解View的直接继承。AnalogClock就是Home Screen上的那个带有两根指针的表盘类

  针对Android底层View的直接构造很多网友没有实战经验,本次Android开发网结合目前平台开源代码一起通过AnalogClock类 来理解View的直接继承。AnalogClock就是Home Screen上的那个带有两根指针的表盘类。它的实现我们直接从开源代码可以了解到:

  public class AnalogClock extends View {

  private Time mCalendar;

  private Drawable mHourHand; //时针

  private Drawable mMinuteHand; //分针

  private Drawable mDial; //表盘背景

  private int mDialWidth; //表盘宽度

  private int mDialHeight; //表盘高度

  private boolean mAttached; //附着状态

  private final Handler mHandler = new Handler(); //定一个Handler类实现更新时间

  private float mMinutes;

  private float mHour;

  private boolean mChanged; //时间是否改变

  public AnalogClock(Context context) {

  this(context, null);

  }

  public AnalogClock(Context context, AttributeSet attrs) {

  this(context, attrs, 0);

  }

  public AnalogClock(Context context, AttributeSet attrs,

  int defStyle) {

  super(context, attrs, defStyle);

  Resources r = mContext.getResources();

  TypedArray a =

  context.obtainStyledAttributes(

  attrs, com.android.internal.R.styleable.AnalogClock, defStyle, 0);

  mDial = a.getDrawable(com.android.internal.R.styleable.AnalogClock_dial); //加载表盘资源

  if (mDial == null) {

  mDial = r.getDrawable(com.android.internal.R.drawable.clock_dial);

  }

  mHourHand = a.getDrawable(com.android.internal.R.styleable.AnalogClock_hand_hour); //加载时针图片资源

  if (mHourHand == null) {

  mHourHand = r.getDrawable(com.android.internal.R.drawable.clock_hand_hour);

  }

  mMinuteHand = a.getDrawable(com.android.internal.R.styleable.AnalogClock_hand_minute); //加载分针图片

  if (mMinuteHand == null) {

  mMinuteHand = r.getDrawable(com.android.internal.R.drawable.clock_hand_minute);

  }

  mCalendar = new Time(); //获取当前系统时间

  mDialWidth = mDial.getIntrinsicWidth(); //获取表盘图片的宽度

  mDialHeight = mDial.getIntrinsicHeight(); //高度,同上

  }

  @Override

  protected void onAttachedToWindow() {

  super.onAttachedToWindow();

  if (!mAttached) {

  mAttached = true;

  IntentFilter filter = new IntentFilter(); //注册一个消息过滤器,获取时间改变、时区改变的action

  filter.addAction(Intent.ACTION_TIME_TICK);

  filter.addAction(Intent.ACTION_TIME_CHANGED);

  filter.addAction(Intent.ACTION_TIMEZONE_CHANGED);

  getContext().registerReceiver(mIntentReceiver, filter, null, mHandler);

  }

  mCalendar = new Time();

  onTimeChanged();

  }

  @Override

  protected void onDetachedFromWindow() {

  super.onDetachedFromWindow();

  if (mAttached) {

  getContext().unregisterReceiver(mIntentReceiver); //反注册消息过滤器

  mAttached = false;

  }

  }

  @Override

  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

  int widthMode = MeasureSpec.getMode(widthMeasureSpec);

  int widthSize = MeasureSpec.getSize(widthMeasureSpec);

  int heightMode = MeasureSpec.getMode(heightMeasureSpec);

  int heightSize = MeasureSpec.getSize(heightMeasureSpec);

  float hScale = 1.0f;

  float vScale = 1.0f;

  if (widthMode != MeasureSpec.UNSPECIFIED && widthSize < mDialWidth) {

  hScale = (float) widthSize / (float) mDialWidth;

  }

  if (heightMode != MeasureSpec.UNSPECIFIED && heightSize < mDialHeight) {

  vScale = (float )heightSize / (float) mDialHeight;

  }

  float scale = Math.min(hScale, vScale);

  setMeasuredDimension(resolveSize((int) (mDialWidth * scale), widthMeasureSpec),

  resolveSize((int) (mDialHeight * scale), heightMeasureSpec));

  }

  @Override

  protected void onSizeChanged(int w, int h, int oldw, int oldh) {

  super.onSizeChanged(w, h, oldw, oldh);

  mChanged = true;

  }

  主要的绘图重写View的onDraw方法,我们可以看到通过canvas实例直接屏幕

  @Override

  protected void onDraw(Canvas canvas) {

  super.onDraw(canvas);

  boolean changed = mChanged;

  if (changed) {

  mChanged = false;

  }

  int availableWidth = mRight - mLeft;

  int availableHeight = mBottom - mTop;

  int x = availableWidth / 2;

  int y = availableHeight / 2;

  final Drawable dial = mDial;

  int w = dial.getIntrinsicWidth();

  int h = dial.getIntrinsicHeight();

  boolean scaled = false;

  if (availableWidth < w || availableHeight < h) {

  scaled = true;

  float scale = Math.min((float) availableWidth / (float) w,

  (float) availableHeight / (float) h);

  canvas.save();

  canvas.scale(scale, scale, x, y);

  }

  if (changed) {

  dial.setBounds(x - (w / 2), y - (h / 2), x + (w / 2), y + (h / 2));

  }

  dial.draw(canvas);

  canvas.save();

  canvas.rotate(mHour / 12.0f * 360.0f, x, y); //计算时针旋转的角度,android123提示就是那个时针图片的旋转角度,直接反应的就是表盘上那个针的时间

  final Drawable hourHand = mHourHand;

  if (changed) {

  w = hourHand.getIntrinsicWidth();

  h = hourHand.getIntrinsicHeight();

  hourHand.setBounds(x - (w / 2), y - (h / 2), x + (w / 2), y + (h / 2));

  }

  hourHand.draw(canvas);

  canvas.restore();

  canvas.save();

  canvas.rotate(mMinutes / 60.0f * 360.0f, x, y); //同理,分针旋转的角度

  final Drawable minuteHand = mMinuteHand;

  if (changed) {

  w = minuteHand.getIntrinsicWidth();

  h = minuteHand.getIntrinsicHeight();

  minuteHand.setBounds(x - (w / 2), y - (h / 2), x + (w / 2), y + (h / 2));

  }

  minuteHand.draw(canvas);

  canvas.restore();

  if (scaled) {

  canvas.restore();

  }

  }

  private void onTimeChanged() { //获取时间改变,计算当前的时分秒

  mCalendar.setToNow();

  int hour = mCalendar.hour;

  int minute = mCalendar.minute;

  int second = mCalendar.second;

  mMinutes = minute + second / 60.0f;

  mHour = hour + mMinutes / 60.0f;

  mChanged = true;

  }

  private final BroadcastReceiver mIntentReceiver = new BroadcastReceiver() { //监听获取时间改变action

  @Override

  public void onReceive(Context context, Intent intent) {

  if (intent.getAction().equals(Intent.ACTION_TIMEZONE_CHANGED)) {

  String tz = intent.getStringExtra("time-zone");

  mCalendar = new Time(TimeZone.getTimeZone(tz).getID());

  }

  onTimeChanged(); //获取新的时间

  invalidate(); //刷新屏幕,强制类调用onDraw方法实现分针时针的走动

  }

  };

  看了本例根据,Android开发很简单吧,感兴趣的网友可以为本程序加入一个秒针,不过Android123提醒网友的是可能对于电池,以及系统运行效 率产生一定的影响,不过作为练习大家可以试一试。

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