我正在编写一个移动应用程序，并通过该按钮的OnClick方法将弹出菜单附加到了ImageButton上。
menu_lilac.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
showPopup(view);
}
});
我正在尝试使其按菜单项重定向到相关的 Activity (在最后的switch语句中)。
我得到的错误是错误:(23，8)错误:MainActivity不是抽象的，并且不会覆盖OnMenuItemClickListener中的抽象方法onMenuItemClick(MenuItem)。
public void showPopup(View view) {
PopupMenu popup = new PopupMenu(this, view);
MenuInflater inflater = popup.getMenuInflater();
inflater.inflate(R.menu.mainmenu, popup.getMenu());
MenuItem item = (MenuItem) popup.getMenu();
popup.show();
//Intent to Tasks Activity
final Intent toTasks = new Intent(this, TasksActivity.class);
//Intent to Distractions Activity
final Intent toDist = new Intent(this, DistractionsActivity.class);
//Intent to Settings Activity
final Intent toSett = new Intent(this, SettingsActivity.class);
popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener(){
@Override
public boolean onMenuItemClick(MenuItem item) {
switch (item.getItemId()) {
case R.id.Home:
return true;
case R.id.Tasks:
startActivity(toTasks);
return true;
case R.id.Distractions:
startActivity(toDist);
return true;
case R.id.Settings:
startActivity(toSett);
return true;
default:
return false;
}
}
});
}
我究竟做错了什么？我尝试以其他方式初始化OnMenuItemClickListener
PopupMenu.OnMenuItemClickListener listener = PopupMenu.OnMenuItemClickListener(){
}
但从不使用监听器，并且在按下任何菜单按钮时应用都会崩溃。
完整的MainActivity类:
import android.app.Activity;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.SystemClock;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.NumberPicker;
import android.widget.PopupMenu;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.ListView;
public class MainActivity extends Activity implements PopupMenu.OnMenuItemClickListener {
//Creation of used objects
//Button, Button, TextView, Handler, AlarmManager, NumberPicker, Pending Intent
//Context, TextView, Button
Button startButton;
Button stopButton;
TextView timerValue;
Handler customHandler = new Handler();
NumberPicker interval_length;
PendingIntent pending_intent;
Context context;
TextView checker;
ImageButton menu_lilac;
Intent toDist;
Intent toSett;
Intent toTasks;
//Creation of variables
long timeInMilliseconds = 0L;
long updatedTime = 0L;
long startTime = 0L;
int picked_value;
private static int minValueInterval = 1;
private static int maxValueInterval = 60;
int final_interval;
//On create function initialises the layout
@Override
protected void onCreate(Bundle savedInstanceState) {
//Creation of main GUI layout
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.context = this;
}
@Override
protected void onStart() {
super.onStart();
//Initialise number picker
interval_length = (NumberPicker) findViewById(R.id.interval_length);
//Set minimum value (minutes)
interval_length.setMinValue(minValueInterval);
//Set maximum value (minutes)
interval_length.setMaxValue(maxValueInterval);
//Set currently displayed value (minutes)
interval_length.setValue(20);
//Initialise listener to listen for a value change on the number picker
interval_length.setOnValueChangedListener(new NumberPicker.OnValueChangeListener() {
@Override
public void onValueChange(NumberPicker picker, int oldVal, int newVal) {
//Replace variable picked_value with the new value of the number picker
picked_value = interval_length.getValue() - 1;
}
});
//Initialise timerValue text box
timerValue = (TextView) findViewById(R.id.timerValue);
//Initialise start button
startButton = (Button) findViewById(R.id.startButton);
//Initialise instance of stop button
stopButton = (Button) findViewById(R.id.stopButton);
//Initialise instance of menu button
menu_lilac = (ImageButton) findViewById(R.id.menu_lilac);
//Initialise checker text box
checker = (TextView) findViewById(R.id.checker);
//Menu button onClickListener
menu_lilac.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
showPopup(view);
}
});
//Start button OnClickListener
startButton.setOnClickListener(new View.OnClickListener() {
//On start begin counting up in milliseconds.
//Reset timer every time Start button is pressed.
public void onClick(View view) {
timerValue.setText("00:00");
startTime = SystemClock.uptimeMillis();
customHandler.postDelayed(updateTimerThread, 0);
//Set text box to print a message displaying when the alarm is for
checker.setText("The alarm has been set for " + picked_value + " minutes from now!");
//Make pop-up toast notification
Toast.makeText(context,"Alarm on!", Toast.LENGTH_LONG).show();
}
});
//Calculation of picked interval length (from minutes) to milliseconds
final_interval = picked_value * 60 * 1000;
if (timerValue.equals(picked_value+":00")) {
alarm_manager.set(AlarmManager.RTC_WAKEUP, timeInMilliseconds, pending_intent);
}
//Initialise Stop button OnClickListener
stopButton.setOnClickListener(new View.OnClickListener() {
//On click stop updating timer thread and reset value to 00:00
public void onClick(View view) {
customHandler.removeCallbacks(updateTimerThread);
timerValue.setText("00:00");
//print message to notify user of alarm being cancelled
checker.setText("The alarm has been cancelled!");
//Make toast notification to say alarm cancelled
Toast.makeText(context,"Alarm off!", Toast.LENGTH_LONG).show();
}
});
}
//Creates a runnable to update the timer
private Runnable updateTimerThread = new Runnable() {
public void run() {
//Takes time in milliseconds from the system clock
timeInMilliseconds = SystemClock.uptimeMillis() - startTime;
updatedTime = timeInMilliseconds;
//Converts milliseconds to seconds and minutes
int secs = (int) (updatedTime / 1000);
int mins = secs / 60;
secs = secs % 60;
int milliseconds = (int) (updatedTime % 1000);
//Updates timerValue to the formatted 00:00 (minutes:seconds)
timerValue.setText(String.format("%02d", mins) + ":"
+ String.format("%02d", secs));
customHandler.postDelayed(this, 0);
}
};
public Runnable showPopup(View view) {
PopupMenu popup = new PopupMenu(this, view);
MenuInflater inflater = popup.getMenuInflater();
inflater.inflate(R.menu.mainmenu, popup.getMenu());
MenuItem item = (MenuItem) popup.getMenu();
popup.show();
//Intent to Tasks Activity
final Intent toTasks = new Intent(this, TasksActivity.class);
//Intent to Distractions Activity
final Intent toDist = new Intent(this, DistractionsActivity.class);
//Intent to Settings Activity
final Intent toSett = new Intent(this, SettingsActivity.class);
popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener(){
@Override
public boolean onMenuItemClick(MenuItem item) {
switch (item.getItemId()) {
case R.id.Home:
return true;
case R.id.Tasks:
startActivity(toTasks);
return true;
case R.id.Distractions:
startActivity(toDist);
return true;
case R.id.Settings:
startActivity(toSett);
return true;
default:
return false;
}
}
});
}
}
最佳答案
我看不出您在 Activity 中实际实现接口PopupMenu.OnMenuItemClickListener的原因，但是如果有原因，则必须实现该接口的方法。
因此，基本上，您在 MainActivity 中使用该方法的must have implementation:
@Override
public boolean onMenuItemClick(MenuItem item) {
return false;
}
也希望您使用Android Studio。它应该告诉您有关错误的信息，如果将指针放在错误上并单击“ALT + ENTER”，您将在菜单中看到实施方法的项目，单击即可解决该问题。