我创建了一个TextView数组，并使用findViewById对其进行了初始化。
声明：-
TextView varTextView1,varTextView2,varTextView3 //declaring the variables for textView components
TextView textViewArray [];
String textViewArrayString [] = new String [] {"varTextView1","varTextView2","varTextView3"}; //justfornames
textViewArray = new TextView[] {varTextView1,varTextView2,varTextView3"};
初始化TextView数组：-
for (TextView element:textViewArray) {
String tempStringOriginal;
tempStringOriginal = textViewArrayString[i].toString(); //getting and storing the textView variable name. not the variable
String tempStringNew = tempStringOriginal.replace("varT","t");
int resID = getResources().getIdentifier(tempStringNew, "id", getPackageName()); //getting the resource id number from the name as android stores it as resource and give it a number
textViewArray[i] = (TextView)findViewById(resID);
i++;
}//foreach loop
用于测试：-
int i=0;
textViewArray[i].setVisibility(View.INVISIBLE); //noerror
textViewArray[i].setVisibility(View.VISIBLE); //noerror
textViewArray[0].getText(); //not working NULLPOINTEREXCEPTION
textViewArray[0].setText("Test"); //not working NULLPOINTEREXCEPTION
我得到的错误：-
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.user.appeggtimer/com.example.user.appeggtimer.MainActivity}: java.lang.NullPointerException: Attempt to read from null array
我不知道这是什么错误，因为.setVisibility可以正常工作，但是.setText显示NullPointerException。
有人可以帮我吗？
===================================
package com.example.user.appeggtimer;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
TextView varTextViewTimer,varTextViewPoints,varTextViewQuestion,varTextViewAnswerA,varTextViewAnswerB,varTextViewAnswerC,varTextViewAnswerD; //declaring the variables for textView components
TextView textViewArray [];
String textViewArrayString [] = new String [] {"varTextViewTimer","varTextViewPoints","varTextViewQuestion","varTextViewAnswerA","varTextViewAnswerB","varTextViewAnswerC","varTextViewAnswerD" };
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
functextViewarray();
funcTextViewArrayPrint();
functextViewarrayInit();
funcVisibilityHideTextView();
funcVisibilityShowTextView();
funcTimeDisplay();
// funcTimeSetAndDisplay();
}
//this function i am not using this was the old one
protected int funcTextViewInit(View view){//initializing the variables with textView
varTextViewTimer = findViewById(R.id.textViewTimer);
varTextViewPoints = findViewById(R.id.textViewPoints);
varTextViewQuestion = findViewById(R.id.textViewQuestion);
varTextViewAnswerA = findViewById(R.id.textViewAnswerA);
varTextViewAnswerB = findViewById(R.id.textViewAnswerB);
varTextViewAnswerC = findViewById(R.id.textViewAnswerC);
varTextViewAnswerD = findViewById(R.id.textViewAnswerD);
return 1;
}//funcTextViewInit
protected void onClickStart(){
funcVisibilityShowTextView();
}//funcOnClickStart
// ==========================TextView=========================//
protected int functextViewarray(){
textViewArray = new TextView[] {varTextViewTimer,varTextViewPoints,varTextViewQuestion,varTextViewAnswerA,varTextViewAnswerB,varTextViewAnswerC,varTextViewAnswerD};
Log.i("functextViewarray","success" );
return 0;
}
protected int functextViewarrayInit(){
int i=0;
for (TextView element:textViewArray) {
String tempStringOriginal;
tempStringOriginal = textViewArrayString[i].toString(); //getting and storing the textView variable name. not the variable
Log.i("regex output",tempStringOriginal );
String tempStringNew = tempStringOriginal.replace("varT","t");
int resID = getResources().getIdentifier(tempStringNew, "id", getPackageName()); //getting the resource id number from the name as android stores it as resource and give it a number
textViewArray[i] = (TextView)findViewById(resID);
i++;
}//foreach loop
return 0;
}//functextViewarrayInit
// =======Hide/Show======
//please_look_at this_func
protected int funcVisibilityShowTextView(){
int i=0;
// varTextViewTimer.setVisibility(View.VISIBLE); without array for each text view
for (TextView element:textViewArray) {
textViewArray[0].setVisibility(View.VISIBLE);
i++;
}//funcVisibilityShowTextView
return 0;
}//funcVisibilityShowTextView
//please_look_at this_func
protected int funcVisibilityHideTextView(){
int i=0;
// varTextViewTimer.setVisibility(View.VISIBLE); without array for each text view
for (TextView element:textViewArray) {
textViewArray[i].setVisibility(View.INVISIBLE);
i++;
}//funcVisibilityHideTextView
return 0;
}//funcVisibilityHideTextView
// ==========================Content display=========================//
protected void funcTimerSet(){
final Handler handler = new Handler();
Runnable run =new Runnable() {
@Override
public void run() {
Log.i("Number of second passed","1");
handler.postDelayed(this,1000);
}
};
handler.post(run);
}//funcTimerSet
//please_look_at this_func
protected void funcTimeDisplay(){}{
int i; //setting to 30 seconds
for(i=30;i>=0;i--){
Log.i("Timer for loop called",Integer.toString(i));
// varTextViewTimer.setText(Integer.toString(i) + "S");
// textViewArray[0].setText(Integer.toString(i));// was getting nullpointer exception
textViewArray[0].getText();
// funcTimerSet();
}//for loop
}//funcTimeDisplay
protected void funcTimeSetAndDisplay(){
final Handler handler = new Handler();
Runnable run =new Runnable() {
@Override
public void run() {
int i=30; //setting to 30 seconds
// for(i=30;i>=0;i--) {
Log.i("Timer for loop called", Integer.toString(i));
// Log.i("Number of second passed", "1");
handler.postDelayed(this, 1000);
// textViewArray[0].setText(Integer.toString(i));
}//forloop
// }
};
handler.post(run);
}
// ==========================Test=========================//
protected void funcTextViewArrayPrint(){
Log.i("prnt 1 el of arr",textViewArrayString[0].toString());
}//funcTextViewArrayPrint
}
=========================
08-20 12:53:36.929 16470-16470/? I/art: Late-enabling -Xcheck:jni
08-20 12:53:36.959 16470-16470/? D/TidaProvider: TidaProvider()
08-20 12:53:37.149 16470-16470/com.example.user.appeggtimer I/InstantRun: starting instant run server: is main process
08-20 12:53:37.249 16470-16470/? I/Timer for loop called: 30
08-20 12:53:37.269 16470-16470/? D/AndroidRuntime: Shutting down VM
08-20 12:53:37.269 16470-16470/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.user.appeggtimer, PID: 16470
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.user.appeggtimer/com.example.user.appeggtimer.MainActivity}: java.lang.NullPointerException: Attempt to read from null array
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2241)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2392)
at android.app.ActivityThread.access$800(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5273)
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:908)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:703)
Caused by: java.lang.NullPointerException: Attempt to read from null array
at com.example.user.appeggtimer.MainActivity.<init>(MainActivity.java:113)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1606)
at android.app.Instrumentation.newActivity(Instrumentation.java:1069)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2231)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2392)
at android.app.ActivityThread.access$800(ActivityThread.java:154)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5273)
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:908)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:703)
08-20 12:53:37.279 16470-16470/? I/Process: Sending signal. PID: 16470 SIG: 9