尝试在 Android Studio 中完成实验。在尝试使用 InputStream、BufferedReader 和 StringBuilder 将文本文件从 Assets 读取到字符串后，字符串显然为空，我似乎无法弄清楚原因。任何帮助表示赞赏。任何帮助是极大的赞赏。文本文件内容为:
Name Test1 Test2 Test3 Final
Adam Anderson 81 90 85 87
Ben Brown 77 80 68 94
Chris Cross 74 80 56 62
Don Dare 86 94 90 89
Eric Earl 96 93 90 98
Fred Foley 79 92 59 86
Gina Gray 80 83 95 87
Holly Hank 74 77 75 78
Ian Ingram 66 64 56 60
Jill Johnson 90 98 78 89
部分内容因尝试测试和修复错误而被注释掉，代码为:
import android.app.AlertDialog;
import android.content.res.AssetManager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class App1Act1 extends AppCompatActivity {
String storage;
int[] testAverages;
int[] testScores;
String[] studentNames;
String[] arrayStorage;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_app1_act1);
/*for(i=0; i<11; i++){
studentNames[i] = inputT.split(" "); */
//error message
AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this);
//StringTokenizer
AssetManager am = getAssets();
try {
InputStream inputT = am.open("grades.txt");
InputStreamReader inputStreamReader = new InputStreamReader(inputT);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
storage = " ";
StringBuilder stringBuilder = new StringBuilder();
while (( (storage = bufferedReader.readLine())) !=null) {
stringBuilder.append(inputT);
}
inputT.close();
}
catch(FileNotFoundException e) {
dlgAlert.setMessage("File was not found, please import file and try again.");
dlgAlert.setTitle("Error Message...");
dlgAlert.setPositiveButton("OK", null);
dlgAlert.setCancelable(true);
dlgAlert.create().show();
}
catch(IOException e){
dlgAlert.setMessage("Oops! Something happened!"); //in the tradition of windows 10
dlgAlert.setTitle("Error Message...");
dlgAlert.setPositiveButton("OK", null);
dlgAlert.setCancelable(true);
dlgAlert.create().show();
}
finally {
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_app1_act1, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onStart () {
super.onStart();
AlertDialog.Builder dlgAlert = new AlertDialog.Builder(this);
if (storage != null) {
arrayStorage = storage.split("\\s+");
}
else {
dlgAlert.setMessage("...crap...");
dlgAlert.setTitle("Error Message...");
dlgAlert.setPositiveButton("OK", null);
dlgAlert.setCancelable(true);
dlgAlert.create().show();
}
/*//array to store names
for (int i=5, s=0; i <= 64; i+=6, s++) {
studentNames[s] = arrayStorage[i] + arrayStorage[i+1];
}
//parse string scores to in array
for(int i=7, p=0; i<=64; i+=6, p+=4) {
testScores[p] = Integer.parseInt(arrayStorage[i]);
testScores[p+1] = Integer.parseInt(arrayStorage[i+1]);
testScores[p+2] = Integer.parseInt(arrayStorage[i+2]);
testScores[p+3] = Integer.parseInt(arrayStorage[i+3]);
}
//calculate and store student averages
for(int i=0, p=0; i<=59; i+=4, p++) {
testAverages[p] = (testScores[i] + testScores[i+1] + testScores[i+2] +testScores[i+3]) / 4;
}
List<String> spinnerArray = new ArrayList<String>(Arrays.asList(studentNames));
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
this, android.R.layout.simple_spinner_item, spinnerArray);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_item);
final Spinner sItems = (Spinner) findViewById(R.id.spinner);
sItems.setAdapter(adapter);
final TextView textView = (TextView) findViewById(R.id.textView);
//set up button for getting grade
Button getGrade = (Button) findViewById(R.id.button);
getGrade.setOnClickListener(new View.OnClickListener() {
String selected = sItems.getSelectedItem().toString();
public void onClick(View v) {
if (selected.equals(studentNames[0])) {
textView.setText(testAverages[0]);
}
else if (selected.equals(studentNames[1])) {
textView.setText(testAverages[1]);
}
else if (selected.equals(studentNames[2])) {
textView.setText(testAverages[2]);
}
else if (selected.equals(studentNames[3])) {
textView.setText(testAverages[3]);
}
else if (selected.equals(studentNames[4])) {
textView.setText(testAverages[4]);
}
else if (selected.equals(studentNames[5])) {
textView.setText(testAverages[5]);
}
else if (selected.equals(studentNames[6])) {
textView.setText(testAverages[6]);
}
else if (selected.equals(studentNames[7])) {
textView.setText(testAverages[7]);
}
else if (selected.equals(studentNames[8])) {
textView.setText(testAverages[8]);
}
else if (selected.equals(studentNames[9])) {
textView.setText(testAverages[9]);
}
}
}); */
}
}
编辑:错误日志:
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: FATAL EXCEPTION: main
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{name.csit.lab4app1/name.csit.lab4app1.App1Act1}: java.lang.NullPointerException
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:99)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.os.Looper.loop(Looper.java:123)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:4627)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at java.lang.reflect.Method.invokeNative(Native Method)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:521)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at dalvik.system.NativeStart.main(Native Method)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: Caused by: java.lang.NullPointerException
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at name.csit.lab4app1.App1Act1.onStart(App1Act1.java:126)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1129)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.Activity.performStart(Activity.java:3781)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2636)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:99)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.os.Looper.loop(Looper.java:123)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:4627)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at java.lang.reflect.Method.invokeNative(Native Method)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at java.lang.reflect.Method.invoke(Method.java:521)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-08 05:34:07.554 273-273/name.csit.lab4app1 E/AndroidRuntime: at dalvik.system.NativeStart.main(Native Method)
编辑:将 System.out.println(storage) 添加到 while 循环后:
10-08 05:46:39.575 273-273/name.csit.lab4app1 I/System.out: Name Test1 Test2 Test3 Final
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Adam Anderson 81 90 85 87
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Ben Brown 77 80 68 94
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Chris Cross 74 80 56 62
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Don Dare 86 94 90 89
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Eric Earl 96 93 90 98
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Fred Foley 79 92 59 86
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Gina Gray 80 83 95 87
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Holly Hank 74 77 75 78
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Ian Ingram 66 64 56 60
10-08 05:46:39.585 273-273/name.csit.lab4app1 I/System.out: Jill Johnson 90 98 78 89
最佳答案
while (( (storage = bufferedReader.readLine())) !=null) {
stringBuilder.append(inputT);
}
这里的inputT不应该被storage取代吗？
while (( (storage = bufferedReader.readLine())) !=null) {
stringBuilder.append(storage);
}
while 循环的条件是“当 storage == null 时，中断”
以下是如何将构建的字符串再次放入存储中
while (( (storage = bufferedReader.readLine())) !=null) {
stringBuilder.append(storage);
}
storage = stringBuilder.toString();
inputT.close();
}
关于java - 尝试读取文件后 rrString 为空，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33007154/