ImageView

<ImageView
        android:src="@drawable/gakki"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:scaleType="centerCrop" />

首先在drawable里面导入图片，gakki.jpg
然后调用时android:src=”@drawable/gakki”，不用加图片的拓展名

这张图转载来自http://blog.csdn.net/u012947056/article/details/46816153
使用scaleType=”centerCrop”时，是无边框，给人身临其境的感觉

google chrome搜索页面中信息时，windows ctr+F
mac cmd+ F

 <LinearLayout
       xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="match_parent">
    <TextView
        android:id="@+id/text_view_id"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:text="@string/hello" />
 </LinearLayout>

  public class MainActivity extends Activity {

    protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         final TextView helloTextView = (TextView) findViewById(R.id.text_view_id);
         helloTextView.setText(R.string.user_greeting);
     }
This code sample demonstrates how to modify the contents of the text view defined in the previous XML layout: