android framework/base 看源码实战:控制Toast显示时长（提供在线看源码地址）

来源/转自：http://www.2cto.com/kf/201410/347560.html

资源提供：

没下载的在线看源码（包括framwork/base）：https://gitorious.org/0xdroid/frameworks_base/source/9c3abacea52f4e03f1de745126a5dd28d269894f:

前言

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。

如果你想要看的是最原汁原味的Toast攻略，请谷歌。

一起分析一下Toast的源码设计吧

Toast的源代码世界
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;
}
瞄了几眼代码，发现Toast显示的布局文件是transient_notification.xml！

怀揣这洋洋得意的心思，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>
接下来看什么呢，肯定是show()方法了。
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；

这个TN是个啥子玩意呢？代码搜索（ctrl + f，输入TN）：

复制代码
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;
}
}
}

这个TN继承了ITransientNotification.Stub，

在源代码中找了一下：ITransientNotification

发现ITransientNotification.aidl

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();
}

回去TN看看他的实现了

复制代码
@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

final Runnable mShow = new Runnable() {
　　@Override
　　public void run() {
　　　　handleShow();
　　}
};

final Runnable mHide = new Runnable() {
　　@Override
　　public void run() {
　　　　handleHide();
　　　　mNextView = null;
　　}
};

现在应该看看handleShow()的实现

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
将目光定位在TN()这个构造方法上

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。

　　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。

自由控制Toast的显示时间
需求： 给应用设置一个较长时间的Toast。

但是不管怎么设置，Toast只能有显示2s和3.5s这两个情况

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，

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;
包访问权限，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，所以还是只能采取其他办法，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：　　

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;
}
}
}