android外存文件读写

1.外存txt文件的读写

2.外存图片文件的读写

需要权限：<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

public class MainActivity extends Activity implements OnClickListener {
    private Button fileSave;
    private Button fileRead;
    private Button picSave;
    private Button picRead;
    private ImageView iv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fileSave = (Button) findViewById(R.id.button1);
        fileRead = (Button) findViewById(R.id.button2);
        picSave = (Button) findViewById(R.id.button3);
        picRead = (Button) findViewById(R.id.button4);
        iv=(ImageView) findViewById(R.id.imageView1);

        fileSave.setOnClickListener(this);
        fileRead.setOnClickListener(this);
        picSave.setOnClickListener(this);
        picRead.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        int id = v.getId();
        switch (id) {
        case R.id.button1:
            FileOutputStream saveTxt = null;
            // 获取外存储卡状态
            if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
                File dir = Environment.getExternalStorageDirectory();
                // 存储一个文本文件
                File file = new File(dir, "cc.txt");
                try {
                    saveTxt = new FileOutputStream(file);
                    saveTxt.write("i am cc!!".getBytes());
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    if (saveTxt != null) {
                        try {
                            saveTxt.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }

            }
            break;
        case R.id.button2:
            // 读取外存文件
            FileInputStream fis = null;
            if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
                File dir = Environment.getExternalStorageDirectory();
                File file = new File(dir, "cc.txt");
                try {
                    fis = new FileInputStream(file);
                    byte[] b = new byte[1024];
                    int len = 0;
                    StringBuilder sb = new StringBuilder();
                    while ((len = fis.read(b)) != -1) {
                        String string = new String(b, 0, len);
                        sb.append(string);
                    }
                    Toast.makeText(this, sb.toString(), Toast.LENGTH_SHORT).show();
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    if (fis != null) {
                        try {
                            fis.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }

            }
            break;
        case R.id.button3:
            // 把图片存入外存
            if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
                Bitmap bm = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                File dir = Environment.getExternalStorageDirectory();
                File file = new File(dir, "cc.jpg");
                FileOutputStream fos = null;
                try {
                    fos = new FileOutputStream(file);
                    bm.compress(CompressFormat.JPEG, 100, fos);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } finally {
                    if (fos != null) {
                        try {
                            fos.close();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }

            }

            break;
        case R.id.button4:
            // 从外存读取图片
            if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
                File dir = Environment.getExternalStorageDirectory();
                File file = new File(dir, "cc.jpg");
                Bitmap bm=BitmapFactory.decodeFile(file.getPath());
                iv.setImageBitmap(bm);
            }
            break;
        default:
            break;
        }
    }

}

布局文件：

<RelativeLayout 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: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="com.example.sdcardfileio.MainActivity" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginLeft="24dp"
        android:text="Button" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button1"
        android:layout_below="@+id/button1"
        android:text="Button" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button2"
        android:layout_below="@+id/button2"
        android:text="Button" />

    <Button
        android:id="@+id/button4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button3"
        android:layout_below="@+id/button3"
        android:text="Button" />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/button4"
        android:layout_marginTop="70dp"
        android:layout_toRightOf="@+id/textView1"
       />

</RelativeLayout>