public class MainActivity extends ActionBarActivity {

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

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    .commit();
        }
    }
    public void call(View v){
        System.out.println("拨打电话。");
        //读取号码
        EditText editText=(EditText) findViewById(R.id.eal);
        String string=editText.getText().toString();
        //拨号
        Intent intent=new Intent();
        intent.setAction(Intent.ACTION_CALL);
        intent.setData(Uri.parse("tel:"+string));
        startActivity(intent);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            return rootView;
        }
        
    }

}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.caller"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="9"
        android:targetSdkVersion="19" />
    <uses-permission 
        android:name="android.permission.CALL_PHONE"
        />
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.caller.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.caller.MainActivity"
    tools:ignore="MergeRootFrame" />

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<TextView 
    android:id="@+id/cal"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/cal"
    />
<EditText 
    android:id="@+id/eal"
    android:inputType="number"
    android:layout_below="@+id/cal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    />
<Button 
    android:id="@+id/bal"
    android:onClick="call"
    android:layout_below="@+id/eal"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/bal"
    />



</RelativeLayout>