对于Android**层View的立即结构许多网民沒有实践经验，此次Android开发设计网融合现阶段服务平台开放源码一起根据AnalogClock类 来了解View的立即承继。AnalogClock便是Home Screen上的那一个含有二根表针的表壳类。它的完成大家立即从开放源码能够掌握到:
public class AnalogClock extends View {
private Time mCalendar;
private Drawable mHourHand; //秒针
private Drawable mMinuteHand; //分针
private Drawable mDial; //表壳情况
private int mDialWidth; //表壳总宽
private int mDialHeight; //表壳高宽比
private boolean mAttached; //粘附情况
private final Handler mHandler = new Handler(); //定一个Handler类完成更新
private float mMinutes;
private float mHour;
private boolean mChanged; //時间是不是更改
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); //载入表壳資源
if (mDial == null) {
mDial = r.getDrawable(com.android.internal.R.drawable.clock_dial);
}
mHourHand = a.getDrawable(com.android.internal.R.styleable.AnalogClock_hand_hour); //载入时针图片資源
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); //载入分针照片
if (mMinuteHand == null) {
mMinuteHand = r.getDrawable(com.android.internal.R.drawable.clock_hand_minute);
}
mCalendar = new Time(); //获得当今时间格式
mDialWidth = mDial.getIntrinsicWidth(); //获得表盘图片的总宽
mDialHeight = mDial.getIntrinsicHeight(); //高宽比，跟上面一样
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
if (!mAttached) {
mAttached = true;
IntentFilter filter = new IntentFilter(); //申请注册一个信息过滤装置，获得時间更改、时区时间更改的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); //反申请注册信息过滤装置
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;
}
关键的制图调用View的onDraw方式 ，我们可以见到根据canvas案例立即显示屏
@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); //测算秒针转动的视角，android123提醒就是那个时针图片的转动视角，立即反映的便是表壳上那一个针的時间
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); //同样，分针转动的视角
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() { //获得時间更改，测算当今的分秒
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() { //监视获得時间更改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(); //获得新的時间
invalidate(); //更新显示屏，强制性类启用onDraw方式 完成分针秒针的行走
}
};
看过本例依据，Android开发设计非常简单吧，有兴趣的网民能够为本程序流程添加一个表针，但是Android123提示网民的是很有可能针对充电电池，及其系统软件运作效 率造成一定的危害，但是做为训练大伙儿能够试一试。
