<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="com.itheima.callphone.MainActivity" >    <EditText        android:id="@+id/et_number"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentLeft="true"        android:layout_alignParentRight="true"        android:layout_alignParentTop="true"        android:ems="10" >        <requestFocus />    </EditText>    <Button        android:id="@+id/bt_dial"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentRight="true"        android:layout_below="@+id/et_number"        android:text="@string/_dial" /></RelativeLayout>

package com.itheima.callphone;import android.content.Intent;import android.net.Uri;import android.os.Bundle;import android.support.v7.app.ActionBarActivity;import android.text.TextUtils;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;import android.widget.Toast;public class MainActivity extends ActionBarActivity implements OnClickListener {    //用于输入电话号码的文本框    private EditText et_number;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        //获得号码文本输入框        et_number = (EditText)findViewById(R.id.et_number);        //获得拨号按钮        Button bt_dial = (Button)findViewById(R.id.bt_dial);        bt_dial.setOnClickListener(this);    }    @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);    }    //实现各种控件的点击事件    @Override    public void onClick(View v) {        switch (v.getId()) {        case R.id.bt_dial:            callPhone();            break;        default:            break;        }    }    //实现拨号操作    private void callPhone() {        //获取号码输入框的号码        String number = et_number.getText().toString().trim();        //进行非空判断        if(TextUtils.isEmpty(number)){            //给用户提示            Toast.makeText(MainActivity.this, "号码不能为空", Toast.LENGTH_LONG).show();        }        //开启拨号服务        Intent intent = new Intent();        intent.setAction(Intent.ACTION_CALL);        intent.setData(Uri.parse("tel:"+number));        startActivity(intent);    }}