一、定义名称strings.xml

<resources>
    <string name="app_name">电话拨号器</string>
    <string name="action_settings">Settings</string>
    <string name="please_enter_phone_number">请输入电话号码</string>
    <string name="call">拨打</string>
</resources>

二、设计拨号界面main.xml

<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"
                tools:context=".MainActivity" >

    <EditText
            android:id="@+id/et_phone_number"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/please_enter_phone_number"
            android:inputType="phone" />

    <Button
            android:id="@+id/btn_dial"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/et_phone_number"
            android:text="@string/call" />

</RelativeLayout>

三、编写MyActivity.java

package com.example.test;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MyActivity extends Activity {
    private Button mDialButton;
    private EditText mNumberEditText;

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

        mDialButton = (Button) findViewById(R.id.btn_dial);
        mDialButton.setOnClickListener(new ButtonClickListener());
    }

    private class ButtonClickListener implements OnClickListener {

        /**
         * 当按钮被点击的时候调用的方法
         */
        @Override
        public void onClick(View v) {
            mNumberEditText = (EditText) MyActivity.this
                    .findViewById(R.id.et_phone_number);
            //获取电话号码
            String number = mNumberEditText.getText().toString().trim();
            // 判断电话号码是否为空
            if (!TextUtils.isEmpty(number)) {
                //意图想干一件什么事情
                Intent intent = new Intent();
                intent.setAction(Intent.ACTION_CALL);
                //数据都是通过Uri进行包装
                intent.setData(Uri.parse("tel:" + number));
                startActivity(intent);
            } else {
                Toast.makeText(MyActivity.this,
                        R.string.please_enter_phone_number, Toast.LENGTH_SHORT)
                        .show();
            }
        }
    }
}

四、AndroidManifest.xml中添加拨号权限

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