android开发篇--准备之android手机拨号器的实现

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android拨号器的实现

首先建立一个myphone的android项目

编写activity_main.xml 文件（页面布局文件）

<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/numbers"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="@string/number"
        android:singleLine="true"
        />
    <Button
        android:id="@+id/btn_call"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/btn_call"
        />
</LinearLayout>
    1.android:layout_width和android:layout_height的属性
    android:layout_width="match_parent"
    android:layout_height="match_parent"
有三个参数
     1>.fill_parent android:layout_width="fill_parent" 在水平方向占满父元素，android:layout_height="fill_parent"在垂直方向上占满父元素
     2>.match_parent 意思和fill_parent一样
     3>.wrap_content 这个组件的android:text中内容长度而决定长短

    2.android:id="@+id/numbers"的意思是给该组件创建一个Id，该id在gen文件下的R.java中，代码如下：

package com.wxw.phone;

public final class R {
    public static final class attr {
    }
    public static final class dimen {
        /** Default screen margins, per the Android Design guidelines.

         Customize dimensions originally defined in res/values/dimens.xml (such as
         screen margins) for sw720dp devices (e.g. 10" tablets) in landscape here.

         */
        public static final int activity_horizontal_margin=0x7f040000;
        public static final int activity_vertical_margin=0x7f040001;
    }
    public static final class drawable {
        public static final int ic_launcher=0x7f020000;
    }
    public static final class id {
        public static final int action_settings=0x7f080002;
        public static final int btn_call=0x7f080001;
      //这是numbers的id
        public static final int numbers=0x7f080000;
    }
    public static final class layout {
        public static final int activity_main=0x7f030000;
    }
    public static final class menu {
        public static final int main=0x7f070000;
    }
    public static final class string {
        public static final int action_settings=0x7f050001;
        public static final int app_name=0x7f050000;
        public static final int btn_call=0x7f050004;
        public static final int hello_world=0x7f050002;
        public static final int number=0x7f050003;
    }
    public static final class style {
        /**
        Base application theme, dependent on API level. This theme is replaced
        by AppBaseTheme from res/values-vXX/styles.xml on newer devices.

            Theme customizations available in newer API levels can go in
            res/values-vXX/styles.xml, while customizations related to
            backward-compatibility can go here.

        Base application theme for API 11+. This theme completely replaces
        AppBaseTheme from res/values/styles.xml on API 11+ devices.

API 11 theme customizations can go here.

        Base application theme for API 14+. This theme completely replaces
        AppBaseTheme from BOTH res/values/styles.xml and
        res/values-v11/styles.xml on API 14+ devices.

API 14 theme customizations can go here.
         */
        public static final int AppBaseTheme=0x7f060000;
        /** Application theme.
All customizations that are NOT specific to a particular API-level can go here.
         */
        public static final int AppTheme=0x7f060001;
    }
}

这就给它一个id public static final int numbers=0x7f080000;

3.android:hint="@string/number"这句要产生一个在文本框中的提示内容如图

4.android:singleLine="true" EditText只显示一行，不能换行。

下面看MainActivity.java
package com.wxw.phone;

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;
import android.app.Activity;
import android.content.Intent;

public class MainActivity extends Activity implements OnClickListener{
    EditText numbers;
    Button btn_call;
@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  numbers=(EditText) findViewById(R.id.numbers);
  btn_call=(Button) findViewById(R.id.btn_call);
  btn_call.setOnClickListener(this);
}
@Override
public void onClick(View v) {
  // TODO Auto-generated method stub
  if (TextUtils.isEmpty(numbers.getText())) {
   Toast.makeText(this, "请输入电话好",Toast.LENGTH_SHORT).show();
  }else{
   Intent intent = new Intent();
   intent.setAction(Intent.ACTION_CALL);
   intent.setData(Uri.parse("tel:"+numbers.getText().toString()));
   startActivity(intent);

  }

}

}

1. setContentView(R.layout.activity_main)这句代码是把activity_main这个加载到这个activity中，只有加载到activity才能显示在页面上，每一个页面就是一个activity。
2. numbers=(EditText) findViewById(R.id.numbers); 中findViewById是activity的方法里面参数是各个组件的id。然后根据各个组件的类型进行强制转换类型。
3. btn_call.setOnClickListener(this);这是给btn_call这个Button组件给了一个点击监听事件；setOnClickListener中的参数是必须是一个实现OnClickListener的类，而MainActivity恰好实现了OnClickListener这个类，实现这个类必须要实现里面的 public void onClick(View v) {}方法，也就是当点击Button时就会之间onClick方法，所以拨号的功能就在这个方法中实现
4. TextUtils.isEmpty(numbers.getText()) android提供了一个工具类TextUtils，其中的isEmpty就是判断参数是否为空。
5. 以下代码就是实现打电话功能
     Intent intent = new Intent();
     intent.setAction(Intent.ACTION_CALL);
     intent.setData(Uri.parse("tel:"+numbers.getText().toString()));
     startActivity(intent);
   首先Intent intent=new Intent（）中文就是意图，你想要干什么，
      intent.setAction(Intent.ACTION_CALL);就是一个动作干什么，给它的就是打电话
     intent.setData(Uri.parse("tel:"+numbers.getText().toString()))就是既然打电话，望哪打给    它一个电话号
    startActivity(intent);启动打电话的activity实现打电话功能

最后千万别忘了权限，对于android开发来说，打电话时必须要给一个打电话的权限，而这个权限是在AndroidManifest.xml中给的具体看代码
<?xml version="1.0" encoding="utf-8"?>
   <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.wxw.phone"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

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

</manifest>
就是这句 <uses-permission android:name="android.permission.CALL_PHONE"/> 给它一个打电话的权限

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