通过意图获取数据并将其显示在列表视图中时应用程序停止
App is getting stopped when getting data through intent and displaying it in listview
我正在开发一个应用程序，我可以在其中将数据从一个 activity 发送到另一个 activity 并在列表视图中显示相同的数据。
我的代码没有错误，我也检查了 Logcat 错误，但没有任何错误，我的应用程序正在关闭。
附上代码供参考。
这是Reminder.java
Reminder.java
public class Reminder extends AppCompatActivity {
ListView listView;
TextView custom_reminder;
ArrayList<String> reminders;
ArrayAdapter<String> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_reminder);
getSupportActionBar().setTitle("Reminders");
getSupportActionBar().setDisplayShowHomeEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
custom_reminder = (TextView) findViewById(R.id.textView3);
listView = (ListView) findViewById(R.id.listView);
reminders = new ArrayList<>();
adapter = new ArrayAdapter<>(Reminder.this, R.layout.reminder_row, R.id.reminder, reminders);
custom_reminder.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(Reminder.this, WorkReminder.class);
startActivity(intent);
}
});
String reminderName = getIntent().getStringExtra("REMINDER_NAME");
reminders.add(reminderName);
listView.setAdapter(adapter);
}
}
这是工作Reminder.java
工作Reminder.java
public class WorkReminder extends AppCompatActivity{
private int notificationId = 1;
EditText reminder_text;
TimePicker timePicker;
Button setReminder, cancel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_work_reminder);
getSupportActionBar().setTitle("Create reminders");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
createNotificationChannel();
reminder_text = (EditText) findViewById(R.id.reminder_text);
timePicker = (TimePicker) findViewById(R.id.timePicker);
setReminder = (Button) findViewById(R.id.set_button);
cancel = (Button) findViewById(R.id.cancel_button);
setReminder.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (reminder_text.getText().toString().isEmpty()){
reminder_text.setError("Fields can't be empty.");
reminder_text.setFocusable(true);
}
else {
Toast.makeText(WorkReminder.this, "Reminder Set!", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(WorkReminder.this, AlarmReceiver.class);
intent.putExtra("notificationId", notificationId);
intent.putExtra("todo", reminder_text.getText().toString());
PendingIntent pendingIntent = PendingIntent.getBroadcast(WorkReminder.this, 0, intent, 0);
AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
int hour = timePicker.getCurrentHour();
int minute = timePicker.getCurrentMinute();
// Create time.
Calendar startTime = Calendar.getInstance();
startTime.set(Calendar.HOUR_OF_DAY, hour);
startTime.set(Calendar.MINUTE, minute);
startTime.set(Calendar.SECOND, 0);
long alarmStartTime = startTime.getTimeInMillis();
// Set alarm.
// set(type, milliseconds, intent)
alarmManager.set(AlarmManager.RTC_WAKEUP, alarmStartTime, pendingIntent);
String reminder_name = reminder_text.getText().toString();
String time = hour + ":" + minute;
Intent intent1 = new Intent(WorkReminder.this, Reminder.class);
intent1.putExtra("REMINDER_NAME", reminder_name);
intent1.putExtra("TIME", time);
startActivity(intent1);
}
}
});
cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(WorkReminder.this, "Reminder cancelled!", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(WorkReminder.this, AlarmReceiver.class);
AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
PendingIntent pendingIntent = PendingIntent.getBroadcast(WorkReminder.this, 0, intent, 0);
alarmManager.cancel(pendingIntent);
}
});
}
private void createNotificationChannel(){
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
CharSequence title = "Reminder!";
String description = "test";
int importance = NotificationManager.IMPORTANCE_HIGH;
NotificationChannel channel = new NotificationChannel("reminder", title, importance);
channel.setDescription(description);
NotificationManager notificationManager = getSystemService(NotificationManager.class);
notificationManager.createNotificationChannel(channel);
}
}
}
reminder_row.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="16dp">
<TextView
android:id="@+id/reminder"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Main Title"
android:textColor="#000"
android:textStyle="bold"
android:layout_margin="0dp"
android:textSize="16sp"/>
<TextView
android:id="@+id/time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Time"
android:textColor="#000"
android:textStyle="bold"
android:layout_marginTop="3dp"
android:textSize="16sp"/>
</LinearLayout>
Logcat
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:445)
at android.widget.ArrayAdapter.getView(ArrayAdapter.java:407)
at android.widget.AbsListView.obtainView(AbsListView.java:2372)
at android.widget.ListView.makeAndAddView(ListView.java:2052)
at android.widget.ListView.fillDown(ListView.java:786)
at android.widget.ListView.fillFromTop(ListView.java:847)
at android.widget.ListView.layoutChildren(ListView.java:1826)
at android.widget.AbsListView.onLayout(AbsListView.java:2171)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1080)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at androidx.appcompat.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:446)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at com.android.internal.policy.DecorView.onLayout(DecorView.java:758)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2484)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2200)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1386)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6733)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
at android.view.Choreographer.doCallbacks(Choreographer.java:723)
at android.view.Choreographer.doFrame(Choreographer.java:658)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
我想做的是从 WorkReminder.java 获取提醒数据并通过 Intent 将其发送到 Reminder.java。在 Reminder.java 中，我使用 listView 来显示相同的数据。
每次用户提醒时，列表视图应该添加它。
您将 "null" 值放入数组适配器字符串中。请在将 reminderName 添加到数组之前检查它是否为 null。
String reminderName = getIntent().getStringExtra("REMINDER_NAME");
if (reminderName != null) {
reminders.add(reminderName);
}
adapter = new ArrayAdapter<>(Reminder.this, R.layout.reminder_row, R.id.reminder, reminders);
listView.setAdapter(adapter);
我正在开发一个应用程序，我可以在其中将数据从一个 activity 发送到另一个 activity 并在列表视图中显示相同的数据。
我的代码没有错误，我也检查了 Logcat 错误，但没有任何错误，我的应用程序正在关闭。
附上代码供参考。
这是Reminder.java
Reminder.java
public class Reminder extends AppCompatActivity {
ListView listView;
TextView custom_reminder;
ArrayList<String> reminders;
ArrayAdapter<String> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_reminder);
getSupportActionBar().setTitle("Reminders");
getSupportActionBar().setDisplayShowHomeEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
custom_reminder = (TextView) findViewById(R.id.textView3);
listView = (ListView) findViewById(R.id.listView);
reminders = new ArrayList<>();
adapter = new ArrayAdapter<>(Reminder.this, R.layout.reminder_row, R.id.reminder, reminders);
custom_reminder.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(Reminder.this, WorkReminder.class);
startActivity(intent);
}
});
String reminderName = getIntent().getStringExtra("REMINDER_NAME");
reminders.add(reminderName);
listView.setAdapter(adapter);
}
}
这是工作Reminder.java
工作Reminder.java
public class WorkReminder extends AppCompatActivity{
private int notificationId = 1;
EditText reminder_text;
TimePicker timePicker;
Button setReminder, cancel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_work_reminder);
getSupportActionBar().setTitle("Create reminders");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
createNotificationChannel();
reminder_text = (EditText) findViewById(R.id.reminder_text);
timePicker = (TimePicker) findViewById(R.id.timePicker);
setReminder = (Button) findViewById(R.id.set_button);
cancel = (Button) findViewById(R.id.cancel_button);
setReminder.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (reminder_text.getText().toString().isEmpty()){
reminder_text.setError("Fields can't be empty.");
reminder_text.setFocusable(true);
}
else {
Toast.makeText(WorkReminder.this, "Reminder Set!", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(WorkReminder.this, AlarmReceiver.class);
intent.putExtra("notificationId", notificationId);
intent.putExtra("todo", reminder_text.getText().toString());
PendingIntent pendingIntent = PendingIntent.getBroadcast(WorkReminder.this, 0, intent, 0);
AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
int hour = timePicker.getCurrentHour();
int minute = timePicker.getCurrentMinute();
// Create time.
Calendar startTime = Calendar.getInstance();
startTime.set(Calendar.HOUR_OF_DAY, hour);
startTime.set(Calendar.MINUTE, minute);
startTime.set(Calendar.SECOND, 0);
long alarmStartTime = startTime.getTimeInMillis();
// Set alarm.
// set(type, milliseconds, intent)
alarmManager.set(AlarmManager.RTC_WAKEUP, alarmStartTime, pendingIntent);
String reminder_name = reminder_text.getText().toString();
String time = hour + ":" + minute;
Intent intent1 = new Intent(WorkReminder.this, Reminder.class);
intent1.putExtra("REMINDER_NAME", reminder_name);
intent1.putExtra("TIME", time);
startActivity(intent1);
}
}
});
cancel.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(WorkReminder.this, "Reminder cancelled!", Toast.LENGTH_SHORT).show();
Intent intent = new Intent(WorkReminder.this, AlarmReceiver.class);
AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
PendingIntent pendingIntent = PendingIntent.getBroadcast(WorkReminder.this, 0, intent, 0);
alarmManager.cancel(pendingIntent);
}
});
}
private void createNotificationChannel(){
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
CharSequence title = "Reminder!";
String description = "test";
int importance = NotificationManager.IMPORTANCE_HIGH;
NotificationChannel channel = new NotificationChannel("reminder", title, importance);
channel.setDescription(description);
NotificationManager notificationManager = getSystemService(NotificationManager.class);
notificationManager.createNotificationChannel(channel);
}
}
}
reminder_row.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="16dp">
<TextView
android:id="@+id/reminder"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Main Title"
android:textColor="#000"
android:textStyle="bold"
android:layout_margin="0dp"
android:textSize="16sp"/>
<TextView
android:id="@+id/time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Time"
android:textColor="#000"
android:textStyle="bold"
android:layout_marginTop="3dp"
android:textSize="16sp"/>
</LinearLayout>
Logcat
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:445)
at android.widget.ArrayAdapter.getView(ArrayAdapter.java:407)
at android.widget.AbsListView.obtainView(AbsListView.java:2372)
at android.widget.ListView.makeAndAddView(ListView.java:2052)
at android.widget.ListView.fillDown(ListView.java:786)
at android.widget.ListView.fillFromTop(ListView.java:847)
at android.widget.ListView.layoutChildren(ListView.java:1826)
at android.widget.AbsListView.onLayout(AbsListView.java:2171)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1080)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at androidx.appcompat.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:446)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at com.android.internal.policy.DecorView.onLayout(DecorView.java:758)
at android.view.View.layout(View.java:19590)
at android.view.ViewGroup.layout(ViewGroup.java:6053)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2484)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2200)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1386)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6733)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
at android.view.Choreographer.doCallbacks(Choreographer.java:723)
at android.view.Choreographer.doFrame(Choreographer.java:658)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
我想做的是从 WorkReminder.java 获取提醒数据并通过 Intent 将其发送到 Reminder.java。在 Reminder.java 中，我使用 listView 来显示相同的数据。
每次用户提醒时，列表视图应该添加它。
您将 "null" 值放入数组适配器字符串中。请在将 reminderName 添加到数组之前检查它是否为 null。
String reminderName = getIntent().getStringExtra("REMINDER_NAME");
if (reminderName != null) {
reminders.add(reminderName);
}
adapter = new ArrayAdapter<>(Reminder.this, R.layout.reminder_row, R.id.reminder, reminders);
listView.setAdapter(adapter);