您好我正在构建一个加载文本文件的Android应用程序，然后允许用户编辑它。我有这个工作。我现在希望能够将该edittext数据保存为设备根目录或SD卡上的新txt文件。到目前为止，这是我的代码：
package com.example.ryan.ciscorouterhelper;
import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
public class MainActivity extends Activity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
EditText LoadedText = new EditText(this);
setContentView(LoadedText);
AssetManager assetManager = getAssets();
InputStream Reader = null;
try {
Reader = assetManager.open("text.txt");
String text = loadTextFile(Reader);
LoadedText.setText(text);
} catch (IOException e) {
LoadedText.setText("Couldn't load file");
} finally {
if (Reader != null)
try {
Reader.close();
} catch (IOException e) {
LoadedText.setText("Couldn't close file");
}
}
}
public String loadTextFile(InputStream Reader) throws IOException {
ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
byte[] bytes = new byte[4096];
int len;
while ((len = Reader.read(bytes)) > 0)
byteStream.write(bytes, 0, len);
return new String(byteStream.toByteArray(), "UTF8");
}
public void saveFile(MenuItem item) {
try {
FileOutputStream fileout=openFileOutput("RouterSetup.txt", MODE_PRIVATE);
OutputStreamWriter outputWriter=new OutputStreamWriter(fileout);
outputWriter.write(LoadedText.getText().toString());
outputWriter.close();
//display file saved message
Toast.makeText(getBaseContext(), "File saved successfully!",
Toast.LENGTH_SHORT).show();
} catch (Exception e) {
e.printStackTrace();
}
}
我在操作栏上有一个按钮来保存文件。以下是menu_main.xml
中的代码<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".MainActivity">
<item android:id="@+id/action_settings" android:title="@string/action_settings"
android:orderInCategory="100" android:showAsAction="never"
/>
<item android:id="@+id/action_save"
android:title="@string/action_save"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:icon="@drawable/ic_save_black_48dp"
android:showAsAction="ifRoom"
android:onClick="saveFile"
/>
</menu>
当应用程序崩溃时，saveFile似乎无法找到edittext loadedtext。任何帮助都会很棒。
编辑：
08-02 21:53:43.985 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at com.example.ryan.ciscorouterhelper.MainActivity.saveFile(MainActivity.java:57)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at java.lang.reflect.Method.invoke(Native Method)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:372)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at android.view.MenuInflater$InflatedOnMenuItemClickListener.onMenuItemClick(MenuInflater.java:254)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:147)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:904)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:894)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at android.widget.ActionMenuView.invokeItem(ActionMenuView.java:587)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at com.android.internal.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:141)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at android.view.View.performClick(View.java:4761)
08-02 21:53:44.024 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at android.view.View$PerformClick.run(View.java:19767)
08-02 21:53:44.025 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at android.os.Handler.handleCallback(Handler.java:739)
08-02 21:53:44.025 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at android.os.Handler.dispatchMessage(Handler.java:95)
08-02 21:53:44.025 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at android.os.Looper.loop(Looper.java:135)
08-02 21:53:44.025 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at android.app.ActivityThread.main(ActivityThread.java:5312)
08-02 21:53:44.025 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at java.lang.reflect.Method.invoke(Native Method)
08-02 21:53:44.025 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at java.lang.reflect.Method.invoke(Method.java:372)
08-02 21:53:44.025 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
08-02 21:53:44.025 1113-1113/com.example.ryan.ciscorouterhelper W/System.err﹕ at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
这些是我在实现下面的修复后现在得到的新错误。不是很擅长调试但看起来这可能是gettext命令的问题？
答案 0 :(得分：1)
在xml文件上设置以下xml代码
<EditText
android:id="@+id/LoadedText "
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="textMultiLine" >
<requestFocus />
</EditText>
请将EditText LoadedText声明为全局变量外侧onCreate()方法，并在onCreate()内定义，如下面的代码
EditText LoadedText;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LoadedText=(EditText) findViewById(R.id.LoadedText);
AssetManager assetManager = getAssets();
InputStream Reader = null;
try {
Reader = assetManager.open("text.txt");
String text = loadTextFile(Reader);
LoadedText.setText(text);
} catch (IOException e) {
LoadedText.setText("Couldn't load file");
} finally {
if (Reader != null)
try {
Reader.close();
} catch (IOException e) {
LoadedText.setText("Couldn't close file");
}
}
}
并解决保存文件的问题使用以下保存功能
public void saveFile(MenuItem item) {
try {
File myFile = new File("/sdcard/RouterSetup.txt");
myFile.createNewFile();
FileOutputStream fOut = new FileOutputStream(myFile);
OutputStreamWriter myOutWriter =
new OutputStreamWriter(fOut);
myOutWriter.append(LoadedText.getText());
myOutWriter.close();
fOut.close();
Toast.makeText(getBaseContext(),
"Done writing SD " + LoadedText.getText() + ".txt",
Toast.LENGTH_SHORT).show();
} catch (Exception e) {
Toast.makeText(getBaseContext(), e.getMessage(),
Toast.LENGTH_SHORT).show();
}
}
并将以下权限设置为AndroidManifest.xml
<uses-permission android:name="android.permission.INTERNET"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>
<uses-permission android:name="android.permission.READ_PHONE_STATE"></uses-permission>