<uses-permission android:name="android.permission.CALL_PHONE" />

 <LinearLayout 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:orientation="vertical"

     tools:context=".MainActivity" >

     <EditText

         android:id="@+id/phoneNumber"

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:inputType="phone" />

     <Button

         android:id="@+id/btn_call"

         android:layout_width="match_parent"

         android:layout_height="wrap_content"

         android:text="打电话" />

 </LinearLayout>

 public class MainActivity extends Activity {

     private EditText Number;

     private Button btn;

     @Override

     protected void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.activity_main);

         Number = (EditText) findViewById(R.id.phoneNumber);

         btn = (Button) findViewById(R.id.btn_call);

         btn.setOnClickListener(new OnClickListener() {

             @Override

             public void onClick(View v) {

                 if (Number.getText().toString().trim().equals("")) {

                     Number.setError("电话号码不能为空");

                 } else {

                     Intent i = new Intent("android.intent.action.CALL", Uri

                             .parse("tel:" + Number.getText().toString().trim()));

                     startActivity(i);

                 }

             }

         });

     }

 }