Android学习数据存储之_文件存储

正在学习android的数据存储，记录分享如下:

效果图如下

内部存储

To create and write a private file to the internal storage:

CallopenFileOutput()with the name of the file and the operating mode. This returns a FileOutputStream.

Write to the file withwrite().
Close the stream withclose().

To read a file from internal storage:

CallopenFileInput()and pass it the name of the file to read. This returns a FileInputStream.

Read bytes from the file with read().
Then close the stream with close().

外部

和内部相比有几点不同

1.查看外部存储设备是否可用，getExternalStorageState()

2.在清单文件中要加上读写外部存储的权限

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

3.指定具体的存储路径，比如用绝对存储路径

File newfile =new File(dir.getAbsolutePath() + "/" + exFileName);

主要代码如下【仅供参考】

public class MainActivity extends ActionBarActivity {private static final String FILE_NAME = "fileInDome.txt";private static final String TAG = "com.example.filestorage.MainActivity";private EditText etInput;private EditText etContent;private static boolean isRbIn = true;private String exFileName = "fileExDome.txt";@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);etInput = (EditText) findViewById(R.id.et_files);etContent = (EditText) findViewById(R.id.et_content);Button btRead = (Button) findViewById(R.id.bt_read);Button btWrite = (Button) findViewById(R.id.bt_write);btRead.setOnClickListener(new btClickListener());btWrite.setOnClickListener(new btClickListener());}private class btClickListener implements OnClickListener {@Overridepublic void onClick(View v) {switch (v.getId()) {case R.id.bt_read:read_files();break;case R.id.bt_write:write_files();break;default:break;}}}public void read_files() {if (isRbIn) {FileInputStream fis = null;try {fis = openFileInput(FILE_NAME);if (fis.available() == 0)return;byte[] readBytes = new byte[fis.available()];while (fis.read(readBytes) != -1);String readContent = new String(readBytes);etContent.setText(readContent);Toast.makeText(this, "文件读取成功，文件长度为：" + readContent.length(), 0).show();fis.close();} catch (Exception e) {e.printStackTrace();}} else {// 外部存储FileInputStream fis =null;Log.i(TAG, "读取外部存储 isExternalStorageWritable");if (isExternalStorageWritable()) {File dir = new File("/sdcard/");Log.i(TAG, "读取外部存储 /sdcard/");if(dir.exists() && dir.canWrite()){Log.i(TAG, "读取外部存储");try {fis = new FileInputStream(dir.getAbsolutePath() + "/" + exFileName);if(fis.available() == 0)return;Log.i(TAG, "" + fis.available());byte[] readBytes =new byte[fis.available()];while(fis.read(readBytes) !=-1);String readContent =new String(readBytes);etContent.setText(readContent);Toast.makeText(this,"从SD卡读取成功，文件长度为：" + readContent.length(), 0).show();etInput.setText("");fis.close();} catch (Exception e) {e.printStackTrace();}}} else {Toast.makeText(this, "外部存储不可写", 0).show();}}}public void write_files() {if (isRbIn) {FileOutputStream fos = null;try {// 内部存储fos = openFileOutput(FILE_NAME, MODE_PRIVATE);String text = etInput.getText().toString();fos.write(text.getBytes());Toast.makeText(this, "文件写入成功，文件长度为：" + text.length(), 0).show();etInput.setText("");} catch (Exception e) {e.printStackTrace();} finally {if (fos != null) {try {fos.flush();fos.close();} catch (Exception e2) {e2.printStackTrace();}}}} else {// 外部存储FileOutputStream fos =null;Log.i(TAG, "写入外部存储 isExternalStorageWritable");if (isExternalStorageWritable()) {File dir = new File("/sdcard/");Log.i(TAG, "写入外部存储 /sdcard/");if(dir.exists() && dir.canWrite()){Log.i(TAG, "写入外部存储");File newfile =new File(dir.getAbsolutePath() + "/" + exFileName);try {fos = new FileOutputStream(newfile);String text = etInput.getText().toString();fos.write(text.getBytes());Toast.makeText(this,"文件写入SD卡成功，文件长度为：" + text.length(), 0).show();etInput.setText("");fos.close();} catch (Exception e) {e.printStackTrace();}}} else {Toast.makeText(this, "外部存储不可写", 0).show();}}}/* Checks if external storage is available for read and write */public boolean isExternalStorageWritable() {String state = Environment.getExternalStorageState();if (Environment.MEDIA_MOUNTED.equals(state)) {return true;}return false;}public void onRadioButtonClicked(View view) {switch (view.getId()) {case R.id.rb_in:Log.i(TAG, "内部存储");isRbIn = true;break;case R.id.rb_ex:Log.i(TAG, "外部存储");isRbIn = false;break;default:break;}}}

参考 https://developer.android.com/

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