不知道为什么不能使width的值随意变大。可以改变width的值在400dp以下，如果超过400dp的话，toast的宽度就固定不变了，怎么才能使其变大呢？
toast的layout是这样的。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    
    <RelativeLayout 
        android:id="@+id/toast_layout_root"
	    android:layout_width="561dp"
	    android:layout_height="121dp"  
	    android:background="@drawable/bg_toast"
	    android:visibility="visible"   >
	    <TextView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:text="@string/hello_world" />
	    </RelativeLayout>

</RelativeLayout>

源代码是这样的

@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		    
		    Toast   sToast = new Toast(getApplication());
	        LayoutInflater inflater = getLayoutInflater();
	        View layout = inflater.inflate(R.layout.activity_main, null);
	        layout.findViewById(R.id.toast_layout_root).setVisibility(View.VISIBLE);
	        int tmp = 370;
	        if(getResources().getDisplayMetrics().densityDpi==160)
	            tmp = 270;
	        sToast.setGravity(Gravity.CENTER, 0, tmp);
	        sToast.setDuration(Toast.LENGTH_LONG);
	        sToast.setView(layout);

	        sToast.show();


	}