All, Just want to be straight with everyone that I have no idea what I am doing lol. But I am having an issue implementing SharedPreferences onPause\onResume in this project, and I am wondering if someone can tell me where I am going wrong.
Error details:
`E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.androidlabs, PID: 2260
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.androidlabs/com.example.androidlabs.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3365)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.pm.ApplicationInfo android.content.Context.getApplicationInfo()' on a null object reference
at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:173)
at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:174)
at android.content.Context.obtainStyledAttributes(Context.java:744)
at androidx.appcompat.app.AppCompatDelegateImpl.createSubDecor(AppCompatDelegateImpl.java:848)
at androidx.appcompat.app.AppCompatDelegateImpl.ensureSubDecor(AppCompatDelegateImpl.java:815)
at androidx.appcompat.app.AppCompatDelegateImpl.findViewById(AppCompatDelegateImpl.java:640)
at androidx.appcompat.app.AppCompatActivity.findViewById(AppCompatActivity.java:259)
at com.example.androidlabs.MainActivity.<init>(MainActivity.java:19)
at java.lang.Class.newInstance(Native Method)
at android.app.AppComponentFactory.instantiateActivity(AppComponentFactory.java:95)
at androidx.core.app.CoreComponentFactory.instantiateActivity(CoreComponentFactory.java:45)
at android.app.Instrumentation.newActivity(Instrumentation.java:1253)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3353)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7656)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) `
Here is my main activity code. I can tell that the issue is coming from onResume (I think!) but no clue why!
`package com.example.androidlabs;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
//initializing variables
Button next = (Button) findViewById(R.id.next);
EditText name = (EditText) findViewById(R.id.name); //initializing variables
public static final String SHARED_PREF = "sharedprefs";
public static final String TEXT = "text";
private String text;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_activity);
next.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
SharedPreferences sh = getSharedPreferences(SHARED_PREF, MODE_PRIVATE);
SharedPreferences.Editor editor = sh.edit();
editor.putString("name", name.getText().toString());
editor.apply();
openNameActivity();
}
});
}
@Override
protected void onResume() {
super.onResume();
SharedPreferences sh = getSharedPreferences(SHARED_PREF, MODE_PRIVATE);
String savedName = sh.getString("name",null);
if (savedName != null){
name.setText(savedName);
}
}
@Override
protected void onPause() {
super.onPause();
SharedPreferences sh = getSharedPreferences(SHARED_PREF, MODE_PRIVATE);
//save the users name in My Shared Pref
SharedPreferences.Editor editor = sh.edit();
editor.putString("name", name.getText().toString());
editor.apply();
}
public void openNameActivity(){
EditText name = (EditText) findViewById(R.id.name);
String nameText = name.getText().toString();
Intent intent = new Intent(MainActivity.this, NameActivity.class);
intent.putExtra("name", nameText);
startActivityForResult(intent, 1);
};
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == 1) {
if(resultCode == RESULT_OK){
int result = data.getIntExtra("namePref", 0);
if(result == 0){
Toast.makeText(MainActivity.this,"Choose a new name", Toast.LENGTH_LONG).show();
}else{
finishAndRemoveTask();
}
}
if(resultCode == RESULT_CANCELED){
Toast.makeText(MainActivity.this,"Something went wrong", Toast.LENGTH_LONG).show();
}
}
}
}`
CodePudding user response：
Your app is crashing when you open your app? It looks like you are doing initialisation of your button and editText at wrong place
can you move below mentioned code to onCreate method and place it below of setContentView method
next = (Button) findViewById(R.id.next);
name = (EditText) findViewById(R.id.name);
and also you will need to declare next and name both variable