我试图从.txt文件中读取一个名称和姓氏到java应用程序中，我尝试使用AssetManager的第一个方法，但是当我输入它时我的应用程序崩溃。
第二种方法是使用输入流，但我得到3个错误：
Description Resource Path Location Type
ByteArrayOutputStream cannot be resolved to a type MainActivity.java /MyInfo/src/com/example/myinfo line 64 Java Problem
ByteArrayOutputStream cannot be resolved to a type MainActivity.java /MyInfo/src/com/example/myinfo line 64 Java Problem
dummytext cannot be resolved or is not a field MainActivity.java /MyInfo/src/com/example/myinfo line 55 Java Problem
MainActivity.java
package com.example.myinfo;
import java.io.IOException;
import java.io.InputStream;
import android.os.Bundle;
import android.content.res.AssetManager;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/*
TextView name = (TextView) findViewById(R.id.name);
AssetManager assetManager = getAssets();
InputStream input;
try {
input = assetManager.open("info.txt");
int size = input.available();
byte[] buffer = new byte[size];
input.read(buffer);
input.close();
// byte buffer into a string
String text = new String(buffer);
nume.setText(text);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
*/
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
TextView dummytext = (TextView) findViewById(R.id.dummytext);
dummytext.setText(readText());
}
private String readText() {
InputStream inputStream = getResources().openRawResource(R.raw.dummytext);
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
int i;
try {
i = inputStream.read();
while(i!=-1){
byteArrayOutputStream.write(i);
i = inputStream.read();
}
inputStream.close();
}catch (IOException e){
e.printStackTrace();
}
return byteArrayOutputStream.toString();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
return rootView;
}
}
}
我的XML是这样的：
<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.myinfo.MainActivity$PlaceholderFragment" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="87dp"
android:text="Adauga Fisier" />
<TextView
android:id="@+id/dummytext"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/nume"
android:layout_below="@+id/nume"
android:layout_marginTop="29dp"
android:text="Prenume"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_alignRight="@+id/button1"
android:layout_marginRight="14dp"
android:layout_marginTop="65dp"
android:textAppearance="?android:attr/textAppearanceLarge" />
</RelativeLayout>
我不明白我做错了什么。 当我运行现在在注释中的代码时，我注意到我进入了Logcat NullPointerException。
logcat的：
04-07 10:06:11.298: I/dalvikvm(275): Could not find method android.content.pm.PackageManager.getActivityLogo, referenced from method android.support.v7.internal.widget.ActionBarView.<init>
04-07 10:06:11.298: W/dalvikvm(275): VFY: unable to resolve virtual method 318: Landroid/content/pm/PackageManager;.getActivityLogo (Landroid/content/ComponentName;)Landroid/graphics/drawable/Drawable;
04-07 10:06:11.298: D/dalvikvm(275): VFY: replacing opcode 0x6e at 0x008b
04-07 10:06:11.308: I/dalvikvm(275): Could not find method android.content.pm.ApplicationInfo.loadLogo, referenced from method android.support.v7.internal.widget.ActionBarView.<init>
04-07 10:06:11.308: W/dalvikvm(275): VFY: unable to resolve virtual method 314: Landroid/content/pm/ApplicationInfo;.loadLogo (Landroid/content/pm/PackageManager;)Landroid/graphics/drawable/Drawable;
04-07 10:06:11.308: D/dalvikvm(275): VFY: replacing opcode 0x6e at 0x0099
04-07 10:06:11.318: D/dalvikvm(275): VFY: dead code 0x008e-0092 in Landroid/support/v7/internal/widget/ActionBarView;.<init> (Landroid/content/Context;Landroid/util/AttributeSet;)V
04-07 10:06:11.318: D/dalvikvm(275): VFY: dead code 0x009c-00a0 in Landroid/support/v7/internal/widget/ActionBarView;.<init> (Landroid/content/Context;Landroid/util/AttributeSet;)V
04-07 10:06:11.488: D/AndroidRuntime(275): Shutting down VM
04-07 10:06:11.488: W/dalvikvm(275): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
04-07 10:06:11.498: E/AndroidRuntime(275): FATAL EXCEPTION: main
04-07 10:06:11.498: E/AndroidRuntime(275): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myinfo/com.example.myinfo.MainActivity}: java.lang.NullPointerException
04-07 10:06:11.498: E/AndroidRuntime(275): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
04-07 10:06:11.498: E/AndroidRuntime(275): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
04-07 10:06:11.498: E/AndroidRuntime(275): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
04-07 10:06:11.498: E/AndroidRuntime(275): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
04-07 10:06:11.498: E/AndroidRuntime(275): at android.os.Handler.dispatchMessage(Handler.java:99)
04-07 10:06:11.498: E/AndroidRuntime(275): at android.os.Looper.loop(Looper.java:123)
04-07 10:06:11.498: E/AndroidRuntime(275): at android.app.ActivityThread.main(ActivityThread.java:4627)
04-07 10:06:11.498: E/AndroidRuntime(275): at java.lang.reflect.Method.invokeNative(Native Method)
04-07 10:06:11.498: E/AndroidRuntime(275): at java.lang.reflect.Method.invoke(Method.java:521)
04-07 10:06:11.498: E/AndroidRuntime(275): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
04-07 10:06:11.498: E/AndroidRuntime(275): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
04-07 10:06:11.498: E/AndroidRuntime(275): at dalvik.system.NativeStart.main(Native Method)
04-07 10:06:11.498: E/AndroidRuntime(275): Caused by: java.lang.NullPointerException
04-07 10:06:11.498: E/AndroidRuntime(275): at com.example.myinfo.MainActivity.onCreate(MainActivity.java:42)
04-07 10:06:11.498: E/AndroidRuntime(275): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-07 10:06:11.498: E/AndroidRuntime(275): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
04-07 10:06:11.498: E/AndroidRuntime(275): ... 11 more
04-07 10:06:18.688: I/Process(275): Sending signal. PID: 275 SIG: 9
答案 0 :(得分：0)
使用此代码
`InputStream input;
AssetManager assetManager = getAssets();
try {
input = assetManager.open("helloworld.txt");
int size = input.available();
byte[] buffer = new byte[size];
input.read(buffer);
input.close();
// byte buffer into a string
String text = new String(buffer);
dummytext.setText(text);
} catch (IOException e) {
e.printStackTrace();
}
`
此代码从资产管理器打开文件的InputStream，从文件内容中获取大小，使用此大小分配字节缓冲区并在此缓冲区中读取文件，之后从缓冲区创建新字符串并将此字符串设置为textview