#2 第二次实验

soft1614080902411/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.edu.hzu.myapplication4">
+
+    <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">
+        <activity android:name=".MainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+        <activity
+            android:name=".Main2Activity"
+            android:label="@string/app_name"
+            android:theme="@style/AppTheme.NoActionBar" />
+        <activity
+            android:name=".Main3Activity"
+            android:label="@string/app_name"
+            android:theme="@style/AppTheme.NoActionBar"></activity>
+    </application>
+
+</manifest>

soft1614080902411/Java/Main2Activity.java

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+package com.example.edu.hzu.myapplication4;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.support.design.widget.FloatingActionButton;
+import android.support.design.widget.Snackbar;
+import android.support.v7.app.AppCompatActivity;
+import android.support.v7.widget.Toolbar;
+import android.view.View;
+import android.widget.Button;
+import android.content.Context;
+import android.os.Bundle;
+import android.os.Environment;
+import android.util.Log;
+import android.view.View;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.TextView;
+import android.widget.Toast;
+import java.io.BufferedInputStream;
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.FileReader;
+import java.io.IOException;
+import com.example.edu.hzu.myapplication4.R;
+
+public class Main2Activity extends AppCompatActivity {
+    public static final String DIRECTORY = "demo";
+    public static final String FILENAME = "file_demo.txt";
+    public static final String TAG = Main2Activity.class.getSimpleName();
+
+    @Override
+
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main2);
+        ((Button) findViewById(R.id.bt2)).setOnClickListener(new View.OnClickListener() {
+
+            @Override
+
+            public void onClick(View view) {
+                String text = ((EditText) findViewById(R.id.edit1)).getText().toString();
+                saveTextIntoInternalStorage(text);
+            }
+
+        });
+        ((Button) findViewById(R.id.bt4)).setOnClickListener(new View.OnClickListener() {
+
+            @Override
+
+            public void onClick(View view) {
+                Intent intent=new Intent(Main2Activity.this,Main3Activity.class);
+                startActivity(intent);
+            }
+        });
+    }
+    // 将文字保存到内部存储
+    private void saveTextIntoInternalStorage(String text) {
+        // 获取内部存储目录
+        File dir = this.getFilesDir();
+        //File dir = getCacheDir();
+        if (dir.isDirectory()) {
+//            dir.mkdir();
+//            dir.mkdirs();
+        }
+        if (dir.isFile()) {
+            // D:/Abc.txt , -> D:/Abc1.txt ->D:/abc.txt
+        }
+        File file = new File(dir, FILENAME);
+//        try {
+//            File = File.createTempFile(FILENAME, null, dir);
+//        } catch (IOException e) {
+//            e.printStackTrace();
+//        }
+        if (file.exists()) { // 判断文件是否存在
+            Log.i(TAG, file.getAbsolutePath());
+            Log.i(TAG, file.length() + ""); // bytes*1024=kb *1024 MB
+            Log.i(TAG, file.isFile() + "");
+            file.canRead();
+            file.canWrite();
+            file.canExecute();
+            file.getFreeSpace();
+            file.getTotalSpace();
+        }
+        FileOutputStream fos = null;  // 字节流  | char | cn : gbk 2 bytes, utf8 3 bytes
+        try { // 使用API打开输出流
+            fos = openFileOutput(FILENAME, MODE_PRIVATE);
+            //FileOutputStream fos = new FileOutputStream(file);
+            fos.write(text.getBytes()); // 写入内容
+            fos.close(); // 关闭流
+        } catch (FileNotFoundException e) {
+            e.printStackTrace();
+        } catch (IOException e) {
+            e.printStackTrace();
+        } finally {
+            try {
+                fos.close();
+            } catch (IOException e) {
+                e.printStackTrace();
+            }
+        }
+        FileReader reader = null; // char
+        try {
+            reader = new FileReader(file.getAbsoluteFile());
+            BufferedReader bReader = new BufferedReader(reader);
+            String line = bReader.readLine();
+            Log.i(TAG, "从文件读取的内容: " + line);
+            bReader.close();
+            reader.close();
+        } catch (FileNotFoundException e) {
+            e.printStackTrace();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        // 显示结果
+        showResult(file.getAbsolutePath());
+        // 删除文件
+        // file.delete();
+        // deleteFile(FILENAME);
+    }
+    // 将文字保存到外部存储
+    private void saveTextIntoExternalStorage(String text) {
+        if (!isExternalStorageWritable()) {
+            Log.e(TAG, "外部存储不可写!");
+            return;
+        }
+        File dir = getPublicExtStorageDir(DIRECTORY, Environment.DIRECTORY_DOWNLOADS);
+        File file = new File(dir, FILENAME);
+        try {
+            FileOutputStream fos = new FileOutputStream(file);
+            fos.write(text.getBytes());
+            fos.close();
+        } catch (FileNotFoundException e) {
+            e.printStackTrace();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        // 显示结果
+        showResult(file.getAbsolutePath());
+    }
+    /* Checks if external storage is available for read and write */
+    private boolean isExternalStorageWritable() {
+        String state = Environment.getExternalStorageState();
+        if (Environment.MEDIA_MOUNTED.equals(state)) {
+            return true;
+        }
+        return false;
+    }
+    /* Checks if external storage is available to at least read */
+    private boolean isExternalStorageReadable() {
+        String state = Environment.getExternalStorageState();
+        if (Environment.MEDIA_MOUNTED.equals(state) ||
+                Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
+            return true;
+        }
+        return false;
+    }
+    // 创建公开的外部存储目录（App卸载时不会删除）
+    private File getPublicExtStorageDir(String dirName, String type) {
+        if (type == null) { // 指定文件类型
+            type = Environment.DIRECTORY_PICTURES;
+        }
+        File dir = new File(Environment //
+                .getExternalStoragePublicDirectory(type), dirName);
+        if (!dir.mkdirs()) {
+            Log.e(TAG, "目录无法创建!");
+        }
+        long freeSpace = dir.getFreeSpace();
+        Log.i(TAG, "剩余空间大小: " + (freeSpace / 1024 / 1024) + "MB");
+        long totalSpace = dir.getTotalSpace();
+        Log.i(TAG, "总空间大小: " + (totalSpace / 1024 / 1024) + "MB");
+        return dir;
+    }
+    // 创建私有的外部存储目录（App卸载时会一同删除）
+    private File getPrivateExtStorageDir(Context context, String dirName, String type) {
+        if (type == null) { // 指定文件类型
+            type = Environment.DIRECTORY_PICTURES;
+        }
+        File file = new File(context //
+                .getExternalFilesDir(type), dirName);
+        if (!file.mkdirs()) {
+            Log.e(TAG, "目录无法创建!");
+        }
+        return file;
+    }
+    private void showResult(String result) {
+        ((TextView) findViewById(R.id.view1)) //
+                .setText(result.toCharArray(), 0, result.length());
+    }
+}

soft1614080902411/Java/Main3Activity.java

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+package com.example.edu.hzu.myapplication4;
+
+import android.os.Bundle;
+import android.support.design.widget.FloatingActionButton;
+import android.support.design.widget.Snackbar;
+import android.support.v7.app.AppCompatActivity;
+import android.support.v7.widget.Toolbar;
+import android.view.View;
+
+public class Main3Activity extends AppCompatActivity {
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main3);
+    }
+
+}

soft1614080902411/Java/MainActivity.java

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+package com.example.edu.hzu.myapplication4;
+
+import android.content.Intent;
+import android.support.v7.app.AppCompatActivity;
+import android.os.Bundle;
+import android.view.View;
+import android.widget.Button;
+
+public class MainActivity extends AppCompatActivity {
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main);
+        Button bt1=(Button)findViewById(R.id.bt1);
+        bt1.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                Intent intent=new Intent(MainActivity.this,Main2Activity.class);
+                startActivity(intent);
+
+            }
+        });
+    }
+}