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IT培训 > 资料库 > Android自定义View实例AnalogClock源码
  • Android自定义View实例AnalogClock源码

    发布:IT培训 来源:资料库 时间:2014-12-29

  • 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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