Android代码题

6个文件

1. MainActivity.java
2. ShowActivity.java
3. activity_main.xml
4. activity_show.xml
5. RebootService.java
6. AndroidManifest.xml

MainActivity.java

package com.hello.myapplication;

import android.content.Intent;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.view.View;
import android.widget.Button;
import android.widget.EditView;

public class MainActivity extends AppCompatActivity {
    EditView mUsername;
    EditView mPassword;
    Button mRegister;
    Intent intent;
    Bundle bundle;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mUsername = (EditView) findViewById(R.id.mUsername);
        mPassword = (EditView) findViewById(R.id.mPassword);
        mRegister = (Button)findViewById(R.id.mRegister);

        mRegister.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                intent = new Intent(MainActivity.this, ShowActivity.class);
                bundle = new Bundle();
                bundle.putString("username", mUsername.getText().toString());
                bundle.putString("password", mPassword.getText().toString());
                intent.putExtras(bundle);
                startActivity(intent);
            }
        });
    }

    @Override
    protected void onDestroy(){
        intent = new Intent(this, RebootService.class);
        startService(intent);
        super.onDestroy();
    }
}

ShowActivity.java

package com.hello.myapplication;


import android.support.v7.app.AppCompatActivity;

import android.widget.TextView;

import android.content.Intent;
import android.os.Bundle;

import org.json.JSONArray;
import org.json.JSONObject;

import java.io.FileInputStream;
import java.io.FileOutputStream;

public class ShowActivity extends AppCompatActivity {
    TextView mShow;

    JSONArray array;
    JSONObject object;

    String str;
    Intent intent;
    Bundle bundle;

    FileInputStream fileIn;
    FileOutputStream fileOut;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_show);
        mShow = (TextView) findViewById(R.id.mShow);

        //读JSON
        array = new JSONArray();
        try{
            fileIn = openFileInput("user.json");
            byte[] buffer = new byte[fileIn.available()];
            fileIn.read(buffer);
            array = new JSONArray(new String(buffer));
            fileIn.close();
        }catch(Exception e){
            e.printStackTrace();
        }

        intent = getIntent();
        bundle = intent.getExtras();

        //写JSON
        try {
            fileOut = openFileOutput("user.json", MODE_PRIVATE);
            object = new JSONObject();
            object.put("username", bundle.getString("username"));
            object.put("password", bundle.getString("password"));
            array.put(object);
            fileOut.write(array.toString().getBytes());
            fileOut.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        //显示已注册的用户
        try{
            str = "所有用户信息\n\n";
            for(int i=0; i<array.length(); i++){
                object = array.getJSONObject(i);
                str += "username: " + object.getString("username") + "\n";
                str += "password: " + object.getString("password") + "\n\n";
            }
            mShow.setText(str);
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <EditText
        android:id="@+id/mUsername"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20dp"
        android:hint="请输入用户名"/>

    <EditText
        android:id="@+id/mPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="numberPassword"
        android:hint="请输入密码"
        android:textSize="20dp" />
    <Button
        android:id="@+id/mRegister"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="注册"/>
</LinearLayout>

activity_show.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".ShowActivity">

    <TextView
        android:id="@+id/mShow"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</LinearLayout>

RebootService.java

package com.hello.myapplication;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;

public class RebootService extends Service {
    Intent intentActivity;
    public RebootService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }
    @Override
    public int onStartCommand(Intent intent, int flags, int startId){
        intentActivity = new Intent(this, MainActivity.class);
        intentActivity.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        startActivity(intentActivity);
        return super.onStartCommand(intent, flags, startId);
    }
}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.hello.myapplication">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <service
            android:name=".RebootService"
            android:enabled="true"
            android:exported="true"></service>

        <activity android:name=".ShowActivity" />
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>