I have been trying for a while now to figure out how to save data on the Android device or even an SD card to be read by the app. So far no luck. I used the Android SAX Parser to read xml from a server just file, and even from the res/raw folder as well. However, my troubles are in writing the xml file itself. This is just a test program, and my problem at the moment is that while trying to create the file, like 26 ( File dataDir = getDir("DataDir",0); ) generates an error. Here's the code below, followed by the logcat. Any and all help, even just in general about file-writing, would be greatly appreciated. Thank you.
MainActivity.java
package sample.matt.filemanip;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import org.xmlpull.v1.XmlSerializer;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.util.Xml;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
TextView tv;
File dataDir = getDir("DataDir",0);
final String fileLoc = dataDir.getPath()+"/stringfile.xml";
private ArrayList<String> strings = new ArrayList<String>();
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
for(int r = 0; r<10; r++)
strings.add("iteration "+r);
tv = (TextView)findViewById(R.id.text_view);
writeXmlToFile();
loadFeed(ParserType.ANDROID_SAX);
}
private void loadFeed(ParserType type){
try {
Log.i("AndroidNews", "ParserType="+type.name());
FeedParser parser = FeedParserFactory.getParser(fileLoc);
strings = parser.parse();
tv.setText(strings.get(0));
} catch (Throwable t){
Log.e("AndroidNews",t.getMessage(),t);
Toast.makeText(MainActivity.this, "An error occured while reading quotes.", Toast.LENGTH_SHORT).show();
}
}
private void writeXmlToFile(){
File newxmlfile = new File(getCacheDir()+"/stringfile.xml");
try{
newxmlfile.createNewFile();
}catch(IOException e){
Log.e("IOException", "exception in createNewFile() method");
}
FileOutputStream fileos = null;
try{
fileos = new FileOutputStream(newxmlfile);
}catch(FileNotFoundException e){
Log.e("FileNotFoundException", "can't create FileOutputStream");
}
XmlSerializer serializer = Xml.newSerializer();
try {
serializer.setOutput(fileos, "UTF-8");
serializer.startDocument("", Boolean.valueOf(true));
//serializer.setFeature("http://xmlpull.org/v1/doc/features.html#indent-output", true);
serializer.startTag("", "root");
for (String str: strings){
serializer.startTag("", "string");
serializer.startTag(null, "content");
serializer.text(str);
serializer.endTag("", "content");
serializer.endTag(null, "string");
}
serializer.endTag(null, "root");
serializer.endDocument();
serializer.flush();
fileos.close();
tv.setText("file has been created");
} catch (Exception e) {
Log.e("Exception","error occurred while creating xml file");
}
}
}
Logcat
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{sample.matt.filemanip/sample.matt.filemanip.MainActivity}: java.lang.NullPointerException
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.os.Handler.dispatchMessage(Handler.java:99)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.os.Looper.loop(Looper.java:123)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.app.ActivityThread.main(ActivityThread.java:4627)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at java.lang.reflect.Method.invokeNative(Native Method)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at java.lang.reflect.Method.invoke(Method.java:521)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:858)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at dalvik.system.NativeStart.main(Native Method)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): Caused by: java.lang.NullPointerException
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.content.ContextWrapper.getDir(ContextWrapper.java:198)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at sample.matt.filemanip.MainActivity.<init>(MainActivity.java:21)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at java.lang.Class.newInstanceImpl(Native Method)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at java.lang.Class.newInstance(Class.java:1429)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
07-13 12:03:02.499: ERROR/AndroidRuntime(7531): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
Thank you for your time, if something is unclear, please ask!
edit: Manifest:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="sample.matt.filemanip"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".MainActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
edit: new logcat error:
07-13 12:44:50.334: ERROR/AndroidNews(7640): Caused by: java.net.MalformedURLException: Protocol not found: /data/data/sample.matt.filemanip/app_DataDir/stringfile.xml
07-13 12:44:50.334: ERROR/AndroidNews(7640): at java.net.URL.<init>(URL.java:275)
07-13 12:44:50.334: ERROR/AndroidNews(7640): at java.net.URL.<init>(URL.java:159)
07-13 12:44:50.334: ERROR/AndroidNews(7640): at sample.matt.filemanip.BaseFeedParser.<init>(BaseFeedParser.java:17)
Don't call the method out of a method. declare File dataDir where you did, and call dataDir = getDir("DataDir",0); inside onCreate. Same for the next statement.
// Snip
File dataDir;
final String fileLoc;
private ArrayList<String> strings = new ArrayList<String>();
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
dataDir = getDir("DataDir",0);
fileLoc = dataDir.getPath()+"/stringfile.xml";
// snap