Android笔记(4)---常用控件(一)

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本文介绍了一个简单的Android应用程序实例，包括两个活动：MainActivity和ResultActivity。通过输入两个数字并点击计算按钮，程序将显示这两个数字的乘积。此外，还介绍了如何使用菜单功能。

常用控件：

---------------------

TextView
EditView
Menu
Button

例子：Activity003

---------------------------------------------------------

MainActivity.java

package com.example.activity003;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
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.TextView;

public class MainActivity extends Activity {

    private EditText num1Et;
    private EditText num2Et;

    private int num1;
    private int num2;

    private int result;

    private TextView menuStatusTv;

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

        num1Et = (EditText) this.findViewById(R.id.num1);
        num2Et = (EditText) this.findViewById(R.id.num2);
        TextView operationTv = (TextView) this.findViewById(R.id.operation);
        Button calcBut = (Button) this.findViewById(R.id.calc);
        menuStatusTv = (TextView) this.findViewById(R.id.menuStatus);
        menuStatusTv.setText("菜单未选择");

        operationTv.setText(R.string.operation);

        calcBut.setText("计算");
        // 以匿名类的方式为按钮添加监听
        calcBut.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View view) {
                String num1Str = num1Et.getText().toString();
                String num2Str = num2Et.getText().toString();

                try {
                    num1 = Integer.parseInt(num1Str);
                } catch (NumberFormatException e) {
                    num1 = 0;
                }

                try {
                    num2 = Integer.parseInt(num2Str);
                } catch (NumberFormatException e) {
                    num2 = 0;
                }
                // 计算
                result = num1 * num2;

                // 将计算结果传递到ResultActivity中
                Intent intent = new Intent();

                intent.putExtra("result", num1 + " * " + num2 + " = " + result);
                intent.setClass(MainActivity.this, ResultActivity.class);
                MainActivity.this.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);
        int group1 = 1;
        int group2 = 2;
        menu.add(group1, 11, 1, "About1");
        menu.add(group1, 12, 2, "Exit1");

        menu.add(group2, 21, 3, "About2");
        menu.add(group2, 22, 4, "Exit2");
        return true;
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        menuStatusTv.setText("您选择了 " + item.getTitle());
        switch (item.getItemId()) {
            case 11:
                // do nothing
                break;
            case 12:
                finish();
                break;
            case 21:
                // do nothing
                break;
            case 22:
                // do nothing
                break;
        }


        return super.onContextItemSelected(item);
    }



}

ResultActivity.java

package com.example.activity003;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class ResultActivity extends Activity {

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

        TextView resultTv = (TextView) this.findViewById(R.id.result);
        Button backBut = (Button) this.findViewById(R.id.back);

        // 获取处理结果
        Intent intent = this.getIntent();
        String result = intent.getStringExtra("result");

        resultTv.setText(result);
        backBut.setText("返回");
        backBut.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View view) {
                Intent intent = new Intent();
                intent.setClass(ResultActivity.this, MainActivity.class);
                ResultActivity.this.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;
    }

}

res/layout/activity_main.xml

<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"
    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=".MainActivity" >

    <TextView
        android:id="@+id/menuStatus"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/num1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="number" />

    <TextView
        android:id="@+id/operation"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/num2"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="number" />

    <Button
        android:id="@+id/calc"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

res/layout/activity_result.xml

<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"
    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=".MainActivity" >

    <TextView
        android:id="@+id/result"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/back"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

res/values/strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Activity003</string>
    <string name="action_settings">Settings</string>
    <string name="hello_world">Hello world!</string>
    <string name="operation">乘以</string>
    <string name="activity_result">计算结果</string>

</resources>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.activity003"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="9" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.activity003.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>
        <activity
            android:name=".ResultActivity"
            android:label="@string/activity_result" >
        </activity>
    </application>

</manifest>

运行结果：

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