1.用内部存储实现文件写入和读取功能

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <EditText
        android:id="@+id/et_1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="输入你想写入的内容"
        android:layout_margin="10dp"/>
    <Button
        android:id="@+id/bt_1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="写入"
        android:layout_margin="5dp"
        android:onClick="click1"/>
    <EditText
        android:id="@+id/et_2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="显示读取的内容"
        android:layout_margin="10dp"/>
    <Button
        android:id="@+id/bt_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="读取"
        android:layout_margin="5dp"
        android:onClick="click2"/>
</LinearLayout>
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

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

        findViewById(R.id.bt_1);
        findViewById(R.id.bt_2);
        EditText editText1=findViewById(R.id.et_1);
        EditText editText2=findViewById(R.id.et_2);
    }

    public void click1(View view){
        EditText editText1=findViewById(R.id.et_1);
        EditText editText2=findViewById(R.id.et_2);
        String fileName="data.txt";
        String content=editText1.getText().toString();
        FileOutputStream fos=null;
        try {
            fos=openFileOutput(fileName,MODE_PRIVATE);
            fos.write(content.getBytes());
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if (fos!=null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        Toast.makeText(MainActivity.this,"保存成功",Toast.LENGTH_SHORT).show();
    }



    public void click2(View view){
       EditText editText2=findViewById(R.id.et_2);
        String content="";
        FileInputStream fis=null;
        try {
            fis=openFileInput("data.txt");
            byte[] buffer=new byte[fis.available()];
            fis.read(buffer);
            content=new String(buffer);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
           if (fis!=null){
               try {
                   fis.close();
               } catch (IOException e) {
                   e.printStackTrace();
               }
           }
        }
       Toast.makeText(MainActivity.this,"读取成功",Toast.LENGTH_SHORT).show();
        editText2.setText(content);
    }
}

第十一,十二周作业_ide

 

2.使用shedpreference实现记住密码功能

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <TextView
        android:id="@+id/tv_1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="账号"
        android:textSize="20dp" />

    <EditText
        android:id="@+id/et_1"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:hint="请输入用户名"
        android:layout_marginLeft="50dp"/>
    <TextView
        android:id="@+id/tv_2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="密码"
        android:textSize="20dp"
        android:layout_marginTop="40dp"
        android:layout_below="@id/tv_1"/>

    <EditText
        android:id="@+id/et_2"
        android:layout_width="200dp"
        android:layout_height="wrap_content"
        android:layout_below="@id/tv_2"
        android:layout_marginLeft="50dp"
        android:layout_marginTop="-40dp"
        android:hint="请输入密码" />

    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/cb_1"
        android:layout_below="@id/et_2"
        android:layout_marginTop="50dp"
        android:layout_marginLeft="40dp"
        android:text="记住密码"/>

    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/cb_2"
        android:layout_below="@id/et_2"
        android:layout_marginTop="50dp"
        android:layout_marginLeft="40dp"
        android:layout_toRightOf="@id/et_2"
        android:text="自动登录"/>
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/btn_1"
        android:text="登录"
        android:layout_toRightOf="@id/cb_2"
        android:layout_below="@id/et_2"
        android:layout_marginTop="60dp" />

</LinearLayout>
package com.example.myapplication_12;

import java.util.Map;

import android.os.Bundle;
import android.app.Activity;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity implements android.view.View.OnClickListener , CompoundButton.OnCheckedChangeListener {

    private EditText et_account;
    private EditText et_password;
    private Button btn_login;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        Map<String, String> userInfo=myApp2.getUserInfo(this);
        if(userInfo!=null){
            et_account.setText(userInfo.get("account"));
            et_password.setText(userInfo.get("password"));
        }
    }
    private void initView() {
        // TODO Auto-generated method stub
        et_account=(EditText)findViewById(R.id.et_1);
        et_password=(EditText)findViewById(R.id.et_2);
        btn_login=(Button)findViewById(R.id.btn_1);
        btn_login.setOnClickListener(this);
        CheckBox cb1=findViewById(R.id.cb_1);
        cb1.setOnCheckedChangeListener(this);
        CheckBox cb2=findViewById(R.id.cb_2);
        cb2.setOnCheckedChangeListener(this);
    }
    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        switch(v.getId()){
            case R.id.btn_1:
                String account=et_account.getText().toString().trim();
                String password=et_password.getText().toString();
                if(TextUtils.isEmpty(account)){
                    Toast.makeText(this, "请输入账号", Toast.LENGTH_SHORT).show();
                    return;
                }
                if(TextUtils.isEmpty(password)){
                    Toast.makeText(this, "请输入密码", Toast.LENGTH_SHORT).show();
                    return;
                }
                Toast.makeText(this, "登录成功", Toast.LENGTH_SHORT).show();

        }

    }

    @Override
    public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
        switch (compoundButton.getId()){
            case R.id.cb_1 :
                String account=et_account.getText().toString().trim();
                String password=et_password.getText().toString();
                boolean isSaveSuccess=myApp2.saveUserInfo(this, account, password);
                if(isSaveSuccess&&b){
                    Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();
                }else{
                    Toast.makeText(this, "保存失败", Toast.LENGTH_SHORT).show();
                    et_account.setText(null);
                    et_password.setText(null);
                }

                break;
            case R.id.cb_2: account=et_account.getText().toString().trim();
                password=et_password.getText().toString();
                if(TextUtils.isEmpty(account)){
                    Toast.makeText(this, "请输入账号", Toast.LENGTH_SHORT).show();
                    return;
                }
                if(TextUtils.isEmpty(password)){
                    Toast.makeText(this, "请输入密码", Toast.LENGTH_SHORT).show();
                    return;
                }
                if(b)
                    Toast.makeText(this, "登录成功", Toast.LENGTH_SHORT).show();
                else{
                    Toast.makeText(this, "请登录", Toast.LENGTH_SHORT).show();
                }

        }
    }
}
package com.example.myapplication_12;
import java.util.HashMap;
import java.util.Map;

import android.content.Context;
import android.content.SharedPreferences;
public class myApp2 {
        public static boolean saveUserInfo(Context context,String account,String password ){
            SharedPreferences sp=context.getSharedPreferences("data", context.MODE_PRIVATE);
            SharedPreferences.Editor editor=sp.edit();
            editor.putString("Username", account);
            editor.putString("pwd", password);
            editor.commit();
            return true;
        }



        public static Map<String, String> getUserInfo(Context context){

            SharedPreferences sp=context.getSharedPreferences("data", context.MODE_PRIVATE);
            String account=sp.getString("Username", null);
            String password=sp.getString("pwd", null);
            Map<String, String> userMap=new HashMap<String,String>();
            userMap.put("account", account);
            userMap.put("password", password);
            return userMap;


        }
}

第十一,十二周作业_ide_02