本文转载于:http://www.cnblogs.com/net168/p/4058193.html
前言
Toast相信大家都不会陌生吧,如果对于Toast不甚了解,可以参考我的上一篇博客《Android:谈一谈安卓应用中的Toast情节》,里面有关于Toast基础比较详细的介绍。但是如果你想要看的是最原汁原味的Toast攻略,我非常建议你:出门右转,谷歌官网,据说是一个非常给力的地儿,一般人我还不告诉他呢。但是!如果官网的开发者指南都满足不了你的胃口的话,那你还是得准备点西瓜瓜子回来吧,搬个板凳坐前排来一起分析一下Toast的源码设计。
Toast的源代码世界
这个故事要从哪里说起呢?话说很久很久以前,程序员菜鸟小明不小心搜索到了Toast这个java文件,顿时小明心跳加速、脸红耳赤的:“这可不是我经常用到的Toast吗?”。怀揣着程序员固有的好奇心的小明点进了这个代码文件,发现了这么一个函数
public static Toast makeText(Context context, CharSequence text, int duration) { Toast result = new Toast(context); LayoutInflater inflate = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); View v = inflate.inflate(com.android.internal.R.layout.transient_notification, null); TextView tv = (TextView)v.findViewById(com.android.internal.R.id.message); tv.setText(text); result.mNextView = v; result.mDuration = duration; return result; }
好眼熟,貌似昨天还刚刚跟它在代码上打过招呼呢。小明顿时有一种很高大上的感觉,这就是传说中的android源代码!
小明瞄了几眼代码,马上总结出两个信息:1、android源码真简单!2、Toast显示的布局文件是transient_notification.xml!
怀揣这洋洋得意的心思,小明在源代码中开始搜索transient_notification.xml,一顿卡死,终于在快放弃的时候给出了结果。
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" android:background="?android:attr/toastFrameBackground"> <TextView android:id="@android:id/message" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:layout_gravity="center_horizontal" android:textAppearance="@style/TextAppearance.Toast" android:textColor="@color/bright_foreground_dark" android:shadowColor="#BB000000" android:shadowRadius="2.75" /> </LinearLayout>
这简单的不像话了!!小明愤怒了。但是愤怒归愤怒,小明还是继续往下看了,接下来看什么呢,肯定是show()方法了。
小明边念念叨叨的:“作为一个二十一世纪的优秀攻城狮,我们需要的是一种探索源代码的情怀。。。。。。”,一边定位到了show()的代码。
public void show() { if (mNextView == null) { throw new RuntimeException("setView must have been called"); } INotificationManager service = getService(); String pkg = mContext.getPackageName(); TN tn = mTN; tn.mNextView = mNextView; try { service.enqueueToast(pkg, tn, mDuration); } catch (RemoteException e) { // Empty } }
这里好像是要先获取一个服务:INotificationManager,然后调用service.enqueueToast(pkg, tn, mDuration)好像是将Toast放到一个队列里面显示吧;小明这么底气不足的理解着。这个TN是个啥子玩意呢?没见过?那就来个第一次约会咯。代码搜索出炉:
private static class TN extends ITransientNotification.Stub { final Runnable mShow = new Runnable() { @Override public void run() { handleShow(); } }; final Runnable mHide = new Runnable() { @Override public void run() { handleHide(); // Don't do this in handleHide() because it is also invoked by handleShow() mNextView = null; } }; private final WindowManager.LayoutParams mParams = new WindowManager.LayoutParams(); final Handler mHandler = new Handler(); int mGravity; int mX, mY; float mHorizontalMargin; float mVerticalMargin; View mView; View mNextView; WindowManager mWM; TN() { // XXX This should be changed to use a Dialog, with a Theme.Toast // defined that sets up the layout params appropriately. final WindowManager.LayoutParams params = mParams; params.height = WindowManager.LayoutParams.WRAP_CONTENT; params.width = WindowManager.LayoutParams.WRAP_CONTENT; params.format = PixelFormat.TRANSLUCENT; params.windowAnimations = com.android.internal.R.style.Animation_Toast; params.type = WindowManager.LayoutParams.TYPE_TOAST; params.setTitle("Toast"); params.flags = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE; } /** * schedule handleShow into the right thread */ @Override public void show() { if (localLOGV) Log.v(TAG, "SHOW: " + this); mHandler.post(mShow); } /** * schedule handleHide into the right thread */ @Override public void hide() { if (localLOGV) Log.v(TAG, "HIDE: " + this); mHandler.post(mHide); } public void handleShow() { if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView + " mNextView=" + mNextView); if (mView != mNextView) { // remove the old view if necessary handleHide(); mView = mNextView; Context context = mView.getContext().getApplicationContext(); if (context == null) { context = mView.getContext(); } mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE); // We can resolve the Gravity here by using the Locale for getting // the layout direction final Configuration config = mView.getContext().getResources().getConfiguration(); final int gravity = Gravity.getAbsoluteGravity(mGravity, config.getLayoutDirection()); mParams.gravity = gravity; if ((gravity & Gravity.HORIZONTAL_GRAVITY_MASK) == Gravity.FILL_HORIZONTAL) { mParams.horizontalWeight = 1.0f; } if ((gravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.FILL_VERTICAL) { mParams.verticalWeight = 1.0f; } mParams.x = mX; mParams.y = mY; mParams.verticalMargin = mVerticalMargin; mParams.horizontalMargin = mHorizontalMargin; if (mView.getParent() != null) { if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this); mWM.removeView(mView); } if (localLOGV) Log.v(TAG, "ADD! " + mView + " in " + this); mWM.addView(mView, mParams); trySendAccessibilityEvent(); } } private void trySendAccessibilityEvent() { AccessibilityManager accessibilityManager = AccessibilityManager.getInstance(mView.getContext()); if (!accessibilityManager.isEnabled()) { return; } // treat toasts as notifications since they are used to // announce a transient piece of information to the user AccessibilityEvent event = AccessibilityEvent.obtain( AccessibilityEvent.TYPE_NOTIFICATION_STATE_CHANGED); event.setClassName(getClass().getName()); event.setPackageName(mView.getContext().getPackageName()); mView.dispatchPopulateAccessibilityEvent(event); accessibilityManager.sendAccessibilityEvent(event); } public void handleHide() { if (localLOGV) Log.v(TAG, "HANDLE HIDE: " + this + " mView=" + mView); if (mView != null) { // note: checking parent() just to make sure the view has // been added... i have seen cases where we get here when // the view isn't yet added, so let's try not to crash. if (mView.getParent() != null) { if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this); mWM.removeView(mView); } mView = null; } } }
乍一看,把小明给虚的,急忙找来大牛程序员帮忙讲解一下。大牛认真过了几眼,咦~其实也不是那么复杂的。这时大牛注意到了这个TN继承了ITransientNotification.Stub,这个类的形式不知道大家还熟悉吗?连小明好像在博客园里面介绍AIDL的文章时懵懵懂懂看到过这种形式的类,可是没等小明反应过来,大牛顺手就在源代码中搜索了一下:ITransientNotification
“果断是AIDL!!”小明惊叹。果然大神跟菜鸟就是不一样,大牛这时打开ITransientNotification瞄一瞄,发现了show()和hide()这两个方法。
package android.app; /** @hide */ oneway interface ITransientNotification { void show(); void hide(); }
“那么应该回去TN看看他的实现了”,大牛跟小明说。
@Override public void show() { if (localLOGV) Log.v(TAG, "SHOW: " + this); mHandler.post(mShow); } @Override public void hide() { if (localLOGV) Log.v(TAG, "HIDE: " + this); mHandler.post(mHide); }
原来是使用handler机制,分别post一个nShow和一个mHide,再接再厉,追踪源码
final Runnable mShow = new Runnable() { @Override public void run() { handleShow(); } }; final Runnable mHide = new Runnable() { @Override public void run() { handleHide(); mNextView = null; } };
小明这次学聪明了,毕竟跟大牛学习比小明整天啃得那些《七天精通Android编程》之类的坑爹书靠谱多了,所以小明跟大牛说,我们应该看看handleShow()的实现,正解!
public void handleShow() { if (localLOGV) Log.v(TAG, "HANDLE SHOW: " + this + " mView=" + mView + " mNextView=" + mNextView); if (mView != mNextView) { // remove the old view if necessary handleHide(); mView = mNextView; Context context = mView.getContext().getApplicationContext(); if (context == null) { context = mView.getContext(); } mWM = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE); // We can resolve the Gravity here by using the Locale for getting // the layout direction final Configuration config = mView.getContext().getResources().getConfiguration(); final int gravity = Gravity.getAbsoluteGravity(mGravity, config.getLayoutDirection()); mParams.gravity = gravity; if ((gravity & Gravity.HORIZONTAL_GRAVITY_MASK) == Gravity.FILL_HORIZONTAL) { mParams.horizontalWeight = 1.0f; } if ((gravity & Gravity.VERTICAL_GRAVITY_MASK) == Gravity.FILL_VERTICAL) { mParams.verticalWeight = 1.0f; } mParams.x = mX; mParams.y = mY; mParams.verticalMargin = mVerticalMargin; mParams.horizontalMargin = mHorizontalMargin; if (mView.getParent() != null) { if (localLOGV) Log.v(TAG, "REMOVE! " + mView + " in " + this); mWM.removeView(mView); } if (localLOGV) Log.v(TAG, "ADD! " + mView + " in " + this); mWM.addView(mView, mParams); trySendAccessibilityEvent(); } }
原来是Toast的视图是通过WindowManager的addView来加载的,小明突然感觉自己向高级程序员迈进了一大步-----“怎么说哥现在也是了解实现原理的人了!”
他们接下来又把邪恶的目光定位在TN()这个构造方法上面
TN() { final WindowManager.LayoutParams params = mParams; params.height = WindowManager.LayoutParams.WRAP_CONTENT; params.width = WindowManager.LayoutParams.WRAP_CONTENT; params.format = PixelFormat.TRANSLUCENT; params.windowAnimations = com.android.internal.R.style.Animation_Toast; params.type = WindowManager.LayoutParams.TYPE_TOAST; params.setTitle("Toast"); params.flags = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE; }
这就是设置Toast中的View的各种位置参数params。
但是小明还是有点不明白,大牛看到小明神游的样子,就给他解释道:
其实Toast的原理是这样的,先通过makeText()实例化出一个Toast,然后调用toast.Show()方法,这时并不会马上显示Toast,而是会实例化一个TN变量,然后通过service.enqueueToast()将其加到服务队列里面去等待显示。在TN中进行调控Toast的显示格式以及里面的hide()、show()方法来控制Toast的出现以及消失,强调一下的是这个队列是系统维护的,我们并不能干涉。
小明若有所思的点点头。。。。。。
自由控制Toast的显示时间
时间就像水,干着干着就干了,撸着撸着就没了,吸着吸着就瘪了。两三天又过去了,突然有一天头儿给小明吩咐了一个活:给应用设置一个较长时间的Toast。这还不简单,小明偷偷在工位上打着瞌睡揉揉眼睛,Toast.setDuration()不就解决了嘛~要几秒就设几秒咯,这还是事儿?但是,谷歌又一次坑了他:因为小明不管怎么设置,Toast只能有显示2s和3.5s这两个情况,这时为啥呢?小明突然想起前些天翻了翻Toast的源码,赶紧去里面找答案
private void scheduleTimeoutLocked(ToastRecord r) { mHandler.removeCallbacksAndMessages(r); Message m = Message.obtain(mHandler, MESSAGE_TIMEOUT, r); long delay = r.duration == Toast.LENGTH_LONG ? LONG_DELAY : SHORT_DELAY; mHandler.sendMessageDelayed(m, delay); }
private static final int LONG_DELAY = 3500; // 3.5 seconds private static final int SHORT_DELAY = 2000; // 2 seconds
我们呢看到这里是使用了handler中的延迟发信息来显示toast的,这里我们也看到了,延迟时间是duration,但是只有两个值:2s和3.5s这两个值,所以我们在之前说过我们设置toast的显示时间是没有任何效果的,所以小明又得去请教大牛了,果然活都不会是那么简单的。。。。。。。
大牛早有研究,他分析道:你还记得我们前些天分析的Toast源代码吗?Toast的显示是首先借助TN类,所有的显示逻辑在这个类中的show方法中,然后再实例一个TN类变量,将传递到一个队列中进行显示,所以我们要向解决这个显示的时间问题,那就从入队列这部给截断,说白了就两点:
1、不让Toast进入队列
2、调用TN类中的hide和show的方法自己控制Toast
但是第一点好实现,第二点让人抓狂了,因为我们看到TN这个类是私有的,所以我们也不能实例化他的对象,但是toast类中有一个实例化对象:tn
final TN mTN;
竟然是包访问权限,大牛一脸淫笑的说,咱们得借助无比强大的反射技术,我们只需要反射出这个变量,然后强暴她一次即可,得到这个变量我们可以得到这个TN类对象了,然后再使用反射获取他的show和hide方法即可,代码如下:
方法一:
public class ToastReflect { private Toast mToast; private Field field; private Object obj; private Method showMethod, hideMethod; private double time; private ToastReflect(Context context, String text, double time){ this.time = time; mToast = Toast.makeText(context, text, Toast.LENGTH_LONG); reflectionTN(); } private void reflectionTN() { try{ field = mToast.getClass().getDeclaredField("mTN"); field.setAccessible(true); obj = field.get(mToast); showMethod = obj.getClass().getDeclaredMethod("show", null); hideMethod = obj.getClass().getDeclaredMethod("hide", null); }catch(Exception e){ e.printStackTrace(); } } public static ToastReflect makeText(Context context, String text, double time){ ToastReflect toastReflect = new ToastReflect(context, text, time); return toastReflect; } private void showToast(){ try{ showMethod.invoke(obj, null); }catch(Exception e){ e.printStackTrace(); } } private void hideToast(){ try{ hideMethod.invoke(obj, null); }catch(Exception e){ e.printStackTrace(); } } public void show(){ showToast(); new Timer().schedule(new TimerTask() { @Override public void run() { hideToast(); } }, (long)(time * 1000)); } }
ps:利用反射来控制Toast的显示时间在高版本会有bug,Android 2.2实测实可以用的,Android 4.0则无法使用。具体原因大牛还在分析。。。。。。
方法二:
但是作为一个通用性软件,对于任何版本都需要支持,所以小明还是只能采取其他办法,说实话,还真发现了一个比较傻瓜的实现。
就是可以利用handler.post结合timer来实现效果,兼容性较好。。利用定时重复show一个Toast就能达到根据特定时间来显示的功能。
public class ToastSimple { private double time; private static Handler handler; private Timer showTimer; private Timer cancelTimer; private Toast toast; private ToastSimple(){ showTimer = new Timer(); cancelTimer = new Timer(); } public void setTime(double time) { this.time = time; } public void setToast(Toast toast){ this.toast = toast; } public static ToastSimple makeText(Context context, String text, double time){ ToastSimple toast1= new ToastSimple(); toast1.setTime(time); toast1.setToast(Toast.makeText(context, text, Toast.LENGTH_SHORT)); handler = new Handler(context.getMainLooper()); return toast1; } public void show(){ toast.show(); if(time > 2){ showTimer.schedule(new TimerTask() { @Override public void run() { handler.post(new ShowRunnable()); } }, 0, 1900); } cancelTimer.schedule(new TimerTask() { @Override public void run() { handler.post(new CancelRunnable()); } }, (long)(time * 1000)); } private class CancelRunnable implements Runnable{ @Override public void run() { showTimer.cancel(); toast.cancel(); } } private class ShowRunnable implements Runnable{ @Override public void run() { toast.show(); } } }
方法三:
这时,大牛也琢磨出一个办法,因为Toast是基于windowManager来显示的,所以完全可以自己写一个自定义的Toast,代码如下
package com.net168.toast; import java.util.Timer; import java.util.TimerTask; import android.content.Context; import android.graphics.PixelFormat; import android.view.Gravity; import android.view.View; import android.view.WindowManager; import android.widget.Toast; public class ToastCustom { private WindowManager wdm; private double time; private View mView; private WindowManager.LayoutParams params; private Timer timer; private ToastCustom(Context context, String text, double time){ wdm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE); timer = new Timer(); Toast toast = Toast.makeText(context, text, Toast.LENGTH_SHORT); mView = toast.getView(); params = new WindowManager.LayoutParams(); params.height = WindowManager.LayoutParams.WRAP_CONTENT; params.width = WindowManager.LayoutParams.WRAP_CONTENT; params.format = PixelFormat.TRANSLUCENT; params.windowAnimations = toast.getView().getAnimation().INFINITE; params.type = WindowManager.LayoutParams.TYPE_TOAST; params.setTitle("Toast"); params.flags = WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE; params.gravity = Gravity.CENTER_HORIZONTAL | Gravity.BOTTOM; params.y = -30; this.time = time; } public static ToastCustom makeText(Context context, String text, double time){ ToastCustom toastCustom = new ToastCustom(context, text, time); return toastCustom; } public void show(){ wdm.addView(mView, params); timer.schedule(new TimerTask() { @Override public void run() { wdm.removeView(mView); } }, (long)(time * 1000)); } public void cancel(){ wdm.removeView(mView); timer.cancel(); } }
PS:上面自定义Toast代码只实现了基本功能,其余功能由于时间关系没有全部实现。
测试代码如下:
public class MainActivity extends ActionBarActivity implements View.OnClickListener{ private EditText edt_duration; private Button btn_toast_simple; private Button btn_toast_reflect; private Button btn_toast_custom; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); edt_duration = (EditText) findViewById(R.id.edt_duration); btn_toast_simple = (Button) findViewById(R.id.btn_toast_simple); btn_toast_reflect = (Button) findViewById(R.id.btn_toast_reflect); btn_toast_custom = (Button) findViewById(R.id.btn_toast_custom); btn_toast_simple.setOnClickListener(this); btn_toast_reflect.setOnClickListener(this); btn_toast_custom.setOnClickListener(this); } @Override public void onClick(View v) { double time = Double.parseDouble((edt_duration.getText().toString())); switch (v.getId()){ case R.id.btn_toast_simple: ToastSimple.makeText(MainActivity.this, "简单Toast,执行时间为:" + time, time).show(); break; case R.id.btn_toast_reflect: ToastReflect.makeText(MainActivity.this, "反射Toast,执行时间为" + time, time).show(); break; case R.id.btn_toast_custom: ToastCustom.makeText(MainActivity.this, "反射Toast,执行时间为" + time, time).show(); break; } } }
限于篇幅,也就懒得讲解了。。。。。。
作者:enjoy风铃
出处:http://www.cnblogs.com/net168/
本文版权归作者和博客园共有,欢迎转载,但未经作者同意必须保留此段声明,且在文章页面明显位置给出原文连接,否则下次不给你转载了。