Android自定義View實例AnalogClock源碼

針對Android底層View的直接構造很多網友沒有實戰(zhàn)經驗，本次Android開發(fā)網結合目前平臺開源代碼一起通過AnalogClock類 來理解View的直接繼承。AnalogClock就是Home Screen上的那個帶有兩根指針的表盤類。它的實現我們直接從開源代碼可以了解到:

public class AnalogClock extends View {

private Time mCalendar;

private Drawable mHourHand; //時針

private Drawable mMinuteHand; //分針

private Drawable mDial; //表盤背景

private int mDialWidth; //表盤寬度

private int mDialHeight; //表盤高度

private boolean mAttached; //附著狀態(tài)

private final Handler mHandler = new Handler(); //定一個Handler類實現更新時間

private float mMinutes;

private float mHour;

private boolean mChanged; //時間是否改變

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); //加載表盤資源

if (mDial == null) {

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

}

mHourHand = a.getDrawable(com.android.internal.R.styleable.AnalogClock_hand_hour); //加載時針圖片資源

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); //加載分針圖片

if (mMinuteHand == null) {

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

}

mCalendar = new Time(); //獲取當前系統(tǒng)時間

mDialWidth = mDial.getIntrinsicWidth(); //獲取表盤圖片的寬度

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

}

@Override

protected void onAttachedToWindow() {

super.onAttachedToWindow();

if (!mAttached) {

mAttached = true;

IntentFilter filter = new IntentFilter(); //注冊一個消息過濾器，獲取時間改變、時區(qū)改變的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); //反注冊消息過濾器

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;

}

主要的繪圖重寫View的onDraw方法，我們可以看到通過canvas實例直接屏幕

@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); //計算時針旋轉的角度，android123提示就是那個時針圖片的旋轉角度，直接反應的就是表盤上那個針的時間

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，分針旋轉的角度

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() { //獲取時間改變，計算當前的時分秒

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() { //監(jiān)聽獲取時間改變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(); //獲取新的時間

invalidate(); //刷新屏幕，強制類調用onDraw方法實現分針時針的走動

}

};

看了本例根據，Android開發(fā)很簡單吧，感興趣的網友可以為本程序加入一個秒針，不過Android123提醒網友的是可能對于電池，以及系統(tǒng)運行效 率產生一定的影響，不過作為練習大家可以試一試。