我试图从位于apps / main / src / asset的txt文件中读取内容。该文本包含以％开头的幸运饼干。但我的主要问题是它打开了文件。在Android Studio中打开文件的正确方法是什么？我创建了资产文件夹并将我的文本文件放在那里。但我不断收到错误。如果有人可以查看代码/错误并告诉我访问该文件的正确方法。我还添加了＆lt; 这是我的代码
package com.example.jorge.whatsyourname;
import android.content.res.AssetManager;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.appindexing.Thing;
import com.google.android.gms.common.api.GoogleApiClient;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Scanner;
import static java.lang.System.in;
public class MainActivity extends AppCompatActivity {
//variables declaration
EditText nameTxt;
EditText lastnameTxt;
EditText dobTxt;
TextView cookieOutTxt;
int random = 0; //generated random number
int max = 0; //value to be assign on execution (number of fortunes)
ArrayList<String> fortunes; //all fortunes will be stored here
//opening text file located in assets directory
AssetManager assetManager = getAssets();
InputStream is = assetManager.open("fortuneCookie.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(is));
public MainActivity() throws IOException {
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//references
nameTxt = (EditText) findViewById(R.id.nameTxt);
lastnameTxt = (EditText) findViewById(R.id.lastnameTxt);
dobTxt = (EditText) findViewById(R.id.dobTxt);
cookieOutTxt = (TextView) findViewById(R.id.cookieOutTxt);
final Button cookieBtn = (Button) findViewById(R.id.cookieBtn);
cookieBtn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
//scan file if line contains % count, else add to fortune arraylist
boolean flag = false;
String phrase = "";
try {
while (br.readLine() != null && !br.readLine().isEmpty()) {
String line = br.readLine();
//System.out.println(line);
if (line.contains("%") && !flag) {
flag = true;
}
else if (line.contains("%") && flag) {
max++;
phrase = "";
}
else {
phrase = phrase + line;
fortunes.add(max, phrase);
}
}
} catch (IOException e) {
e.printStackTrace();
}
//generating a random fortune
random = (int) (Math.random() * max + 1);
//printing output to screen
cookieOutTxt.setText(fortunes.get(random));
}
});
}
public Action getIndexApiAction() {
Thing object = new Thing.Builder()
.setName("Main Page") // TODO: Define a title for the content shown.
// TODO: Make sure this auto-generated URL is correct.
.setUrl(Uri.parse("http://[ENTER-YOUR-URL-HERE]"))
.build();
return new Action.Builder(Action.TYPE_VIEW)
.setObject(object)
.setActionStatus(Action.STATUS_TYPE_COMPLETED)
.build();
}
}
错误日志
adb shell am start -n "com.example.jorge.whatsyourname/com.example.jorge.whatsyourname.MainActivity" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Client not ready yet..Waiting for process to come online
Connected to process 1573 on device Nexus_5_API_22 [emulator-5554]
I/art: Not late-enabling -Xcheck:jni (already on)
D/AndroidRuntime: Shutting down VM
--------- beginning of crash
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.jorge.whatsyourname, PID: 1573
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.jorge.whatsyourname/com.example.jorge.whatsyourname.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.AssetManager android.content.Context.getAssets()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2236)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.AssetManager android.content.Context.getAssets()' on a null object reference
at android.content.ContextWrapper.getAssets(ContextWrapper.java:80)
at com.example.jorge.whatsyourname.MainActivity.<init>(MainActivity.java:40)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1066)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2226)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5257)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
I/Process: Sending signal. PID: 1573 SIG: 9
Application terminated.
另外我在app.iml文件中有这三行
<option name="MANIFEST_FILE_RELATIVE_PATH" value="/src/main/AndroidManifest.xml" />
<option name="RES_FOLDER_RELATIVE_PATH" value="/src/main/res" />
<option name="RES_FOLDERS_RELATIVE_PATH" value="file://$MODULE_DIR$/src/main/res" />
<option name="ASSETS_FOLDER_RELATIVE_PATH" value="/src/main/assets" />
这个在我的＆＃34; Fortune Cookie.iml＆＃34;文件
<option name="ASSETS_FOLDER_RELATIVE_PATH" value="/src/main/assets" />
答案 0 :(得分：0)
在implements Serializable之前，通常在Activity之后调用从onCreate()或其超类继承的方法。
所以，替换：
super.onCreate()使用：
AssetManager assetManager = getAssets();
InputStream is = assetManager.open("fortuneCookie.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(is));
并将这些行放在AssetManager assetManager;
InputStream is;
BufferedReader br;
之后：
super.onCreate()