Programming Tutorials

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Reading and Writing a file to SD card sample program in Android

By: Ashley in Android Tutorials on 2011年07月03日 [フレーム]

This sample android program shows you how write and read a file from SD Card in Android. In this program four buttons are shown and a Edit box. When you type some text into the edit box and click, Save to SD Card button, the text is saved to a text file and saved to the SD Card. When you click clear button, the edit box contents are cleared. When you click, Read Sd card button the file is read from the SD card and the contents are copied to the edit box.

The FileDemo2.java file is as follows:

package com.javasamples;

import java.io.*;
import android.app.Activity;
import android.os.Bundle;
import android.view.*;
import android.view.View.OnClickListener;
import android.widget.*;
public class FileDemo2 extends Activity {
	// GUI controls
	EditText txtData;
	Button btnWriteSDFile;
	Button btnReadSDFile;
	Button btnClearScreen;
	Button btnClose;
	@Override
	public void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.main);
	// bind GUI elements with local controls
	txtData = (EditText) findViewById(R.id.txtData);
	txtData.setHint("Enter some lines of data here...");
	btnWriteSDFile = (Button) findViewById(R.id.btnWriteSDFile);
	btnWriteSDFile.setOnClickListener(new OnClickListener() {
	public void onClick(View v) {
		// write on SD card file data in the text box
		try {
			File myFile = new File("/sdcard/mysdfile.txt");
			myFile.createNewFile();
			FileOutputStream fOut = new FileOutputStream(myFile);
			OutputStreamWriter myOutWriter = 
									new OutputStreamWriter(fOut);
			myOutWriter.append(txtData.getText());
			myOutWriter.close();
			fOut.close();
			Toast.makeText(getBaseContext(),
					"Done writing SD 'mysdfile.txt'",
					Toast.LENGTH_SHORT).show();
		} catch (Exception e) {
			Toast.makeText(getBaseContext(), e.getMessage(),
					Toast.LENGTH_SHORT).show();
		}
	}// onClick
	}); // btnWriteSDFile
		btnReadSDFile = (Button) findViewById(R.id.btnReadSDFile);
		btnReadSDFile.setOnClickListener(new OnClickListener() {
		public void onClick(View v) {
			// write on SD card file data in the text box
		try {
			File myFile = new File("/sdcard/mysdfile.txt");
			FileInputStream fIn = new FileInputStream(myFile);
			BufferedReader myReader = new BufferedReader(
					new InputStreamReader(fIn));
			String aDataRow = "";
			String aBuffer = "";
			while ((aDataRow = myReader.readLine()) != null) {
				aBuffer += aDataRow + "\n";
			}
			txtData.setText(aBuffer);
			myReader.close();
			Toast.makeText(getBaseContext(),
					"Done reading SD 'mysdfile.txt'",
					Toast.LENGTH_SHORT).show();
		} catch (Exception e) {
			Toast.makeText(getBaseContext(), e.getMessage(),
					Toast.LENGTH_SHORT).show();
		}
		}// onClick
		}); // btnReadSDFile
		btnClearScreen = (Button) findViewById(R.id.btnClearScreen);
		btnClearScreen.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				// clear text box
				txtData.setText("");
			}
		}); // btnClearScreen
		btnClose = (Button) findViewById(R.id.btnClose);
		btnClose.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				// clear text box
				finish();
			}
		}); // btnClose
	}// onCreate
}// AndSDcard

The output of this program will be as shown in the android emulator below.

The main.xml file in your res/layout folder is as follows:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
android:id="@+id/widget28"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#ff0000ff"
android:orientation="vertical"
xmlns:android="http://schemas.android.com/apk/res/android"
>
<EditText
android:id="@+id/txtData"
android:layout_width="fill_parent"
android:layout_height="180px"
android:textSize="18sp" />
<Button
android:id="@+id/btnWriteSDFile"
android:layout_width="143px"
android:layout_height="44px"
android:text="1. Write SD File" />
<Button
android:id="@+id/btnClearScreen"
android:layout_width="141px"
android:layout_height="42px"
android:text="2. Clear Screen" />
<Button
android:id="@+id/btnReadSDFile"
android:layout_width="140px"
android:layout_height="42px"
android:text="3. Read SD File" />
<Button
android:id="@+id/btnClose"
android:layout_width="141px"
android:layout_height="43px"
android:text="4. Close" />
</LinearLayout>

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