Toast

Toast的基本原理其实就是将一个View添加到WindowManager中，让WindowManager来把View显示出来。（WindowManager可以将View显示在任何地方，任何Activity之上）


Toast的默认属性

//对其方式为：水平居中，并在底部
mGravity=Gravtiy.CENTER_HORIZONTAL|Gravtiy.BOTTOM;

mX=0;
mY=context.getResources().getDimensionPixelSize(com.android.internal.R.dimen.toast_y_offset);

mHorizontalMargin=0;
mVerticalMargin=0;

所以用Toast.makeText(getApplicationContext(),R.string.text,Toast.LENGTH_SHORT).show();生成的Toast总是处在底部水平居中的位置

在指定x, y处显示Toast

//在(50,100)处显示Toast
Toasttoast=Toast.makeText(getApplicationContext(),"toastuse",Toast.LENGTH_SHORT);
toast.setGravity(Gravity.TOP|Gravity.LEFT,50,100);
toast.show();

//如果使用Gravity.NO_GRAVITY，后面的x,y就是相对于屏幕的中心点的（估计android是默认这么处理的）
Toasttoast=Toast.makeText(getApplicationContext(),"toastuse",Toast.LENGTH_SHORT);
toast.setGravity(Gravity.NO_GRAVITY,50,100);
toast.show();

//用margin来控制toast的位置
Toasttoast=Toast.makeText(getApplicationContext(),"toastuse",Toast.LENGTH_SHORT);
toast.setGravity(Gravity.LEFT|Gravity.TOP,0,0);
//leftMargin,topMargin分别是容器width,height的%多少(这里是10%和20%)
toast.setMargin(0.1F,0.2F);
toast.show();

指定View的Toast

//布局xml：R.layout.toast
<Button
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@android:id/message"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>


Toasttoast=newToast(getApplicationContext());
toast.setView(LayoutInflater.from(getApplicationContext()).inflate(R.layout.toast,null));
toast.setText("toastuse");
//Button是否fill_parent是由gravity控制的,xml中的不起任何作用
toast.setGravity(toast.getGravity()|Gravity.FILL_HORIZONTAL,
toast.getXOffset(),toast.getYOffset());
toast.setDuration(Toast.LENGTH_SHORT);
toast.show();

Toast部分源码

//Toast的构造器只设置了mY这个属性。mNextView,mDuration都没有设置(用makeText的话，这两个属性会设置)
publicToast(Contextcontext){
mContext=context;
mTN=newTN();
mY=context.getResources().getDimensionPixelSize(com.android.internal.R.dimen.toast_y_offset);
}

//setText方法，需要将显示text的view的id设为@android:id/message，否则会抛RuntimeException
publicvoidsetText(CharSequences){
if(mNextView==null){
thrownewRuntimeException("ThisToastwasnotcreatedwithToast.makeText()");
}
TextViewtv=(TextView)mNextView.findViewById(com.android.internal.R.id.message);
if(tv==null){
thrownewRuntimeException("ThisToastwasnotcreatedwithToast.makeText()");
}
tv.setText(s);
}

一直显示的Toast
实现原理是：在Toast隐藏之前，再show一个相同的Toast，来实现长显示的假象

privateclassToastWrapper{
privateToastmToast;

privateHandlermHandler;

privateRunnablemShowToast=newRunnable(){
@Override
publicvoidrun(){
continueShow();
}
};

privatebooleanmCancelled=true;

publicToastWrapper(Contextctxt){
this(ctxt,newHandler());
}

publicToastWrapper(Contextctxt,Handlerhandler){
mToast=Toast.makeText(ctxt,null,Toast.LENGTH_SHORT);
mHandler=handler;
}

publicToastgetToast(){
returnmToast;
}

publicvoidshowUntilCancel(){
if(mCancelled){
mCancelled=false;
mToast.setDuration(Toast.LENGTH_LONG);
continueShow();
}
}

publicvoidcancel(){
mCancelled=true;
mToast.cancel();
}

privatevoidcontinueShow(){
if(mCancelled){
return;
}
mToast.show();
mHandler.postDelayed(mShowToast,3000);
}
}

使用ToastWrapper

//一直显示的toast
toastWrapper=newToastWrapper(getApplicationContext());
Toasttoast=toastWrapper.getToast();
toast.setText("toastwrapper");

//...

Buttonbutton=newButton(getApplicationContext());
button.setText("一直显示toast");
button.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewview){
toastWrapper.showUntilCancel();
}
});

Buttonbutton=newButton(getApplicationContext());
button.setText("隐藏toast");
button.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewview){
toastWrapper.cancel();
}
});



//一搬的toast
Buttonbutton=newButton(getApplicationContext());
button.setText("一般的toast");
button.setOnClickListener(newView.OnClickListener(){
@Override
publicvoidonClick(Viewview){
Toasttoast=toastWrapper.getToast();
toast.setDuration(Toast.LENGTH_SHORT);
toast.show();
}
});
if(phoneIsInUse())
{
newThread(newRunnable(){
publicvoidrun(){
Looper.prepare();
Toast
.makeText(
VuiService.this,
"请结束通话后再试",Toast.LENGTH_LONG).show();
Looper.loop();
}
}).start();
return;
}