后退按钮 - Android工作室
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我有一个导航抽屉,我正在尝试用抽屉中选择的活动中的后退按钮实现操作栏(第二个活动)。我尝试将[getSupportActionBar()...]放在第二个活动的第一个Override中,但是当我从抽屉中选择活动时,它会让我崩溃。
谢谢
这是我的第一个活动
package com.progetto.app;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.NavigationView;
import android.support.design.widget.Snackbar;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
public class Alarm extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_alarm);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.addDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
}
@Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.home, 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);
}
@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
// Handle navigation view item clicks here.
int id = item.getItemId();
switch (id) {
case R.id.nav_home:
Intent h = new Intent(Alarm.this, Home.class);
startActivity(h);
break;
case R.id.nav_bt:
Intent i = new Intent(Alarm.this, BluetoothActivitySetting.class);
startActivity(i);
break;
case R.id.nav_alarm:
Intent g = new Intent(Alarm.this, AlarmActivity.class);
startActivity(g);
break;
case R.id.nav_tips:
Intent s = new Intent(Alarm.this, Tips.class);
startActivity(s);
break;
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
}
这是我的第二项活动
package com.progetto.app;
import android.annotation.TargetApi;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.TimePicker;
import java.util.Calendar;
import java.util.Random;
import android.annotation.TargetApi;
import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.TimePicker;
import android.widget.Toast;
import java.util.Calendar;
public class AlarmActivity extends AppCompatActivity {
//to make our alarm manager
AlarmManager alarm_manager;
TimePicker alarm_timepicker;
TextView update_text;
Context context;
PendingIntent pending_intent;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_alarm2);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
this.context = this;
// initialize our alarm manager
alarm_manager = (AlarmManager) getSystemService(ALARM_SERVICE);
//initialize our timepicker
alarm_timepicker = (TimePicker) findViewById(R.id.time_picker);
//initialize our text update box
update_text = (TextView) findViewById(R.id.update_text);
// create an instance of a calendar
final Calendar calendar = Calendar.getInstance();
// create an intent to the Alarm Receiver class
final Intent my_intent = new Intent(this.context, Alarm_Receiver.class);
// initialize start button
Button alarm_on = (Button) findViewById(R.id.alarm_on);
// create an onClick listener to start the alarm
alarm_on.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// setting calendar instance with the hour and minute that we picked
// on the time picker
calendar.set(Calendar.HOUR_OF_DAY, alarm_timepicker.getHour());
calendar.set(Calendar.MINUTE, alarm_timepicker.getMinute());
// get the int values of the hour and minute
int hour = alarm_timepicker.getHour();
int minute = alarm_timepicker.getMinute();
// convert the int values to strings
String hour_string = String.valueOf(hour);
String minute_string = String.valueOf(minute);
// method that changes the update text Textbox
set_alarm_text("Alarm set to: " + hour_string + ":" + minute_string);
// put in extra string into my_intent
// tells the clock that you pressed the "alarm on" button
my_intent.putExtra("extra", "alarm on");
// create a pending intent that delays the intent
// until the specified calendar time
pending_intent = PendingIntent.getBroadcast(AlarmActivity.this, 0,
my_intent, PendingIntent.FLAG_UPDATE_CURRENT);
// set the alarm manager
alarm_manager.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(),
pending_intent);
}
});
// initialize the stop button
Button alarm_off = (Button) findViewById(R.id.alarm_off);
// create an onClick listener to stop the alarm or undo an alarm set
alarm_off.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// method that changes the update text Textbox
set_alarm_text("Alarm off!");
// cancel the alarm
alarm_manager.cancel(pending_intent);
my_intent.putExtra("extra", "alarm off");
// stop the ringtone
sendBroadcast(my_intent);
}
});
}
private void set_alarm_text(String output) {
update_text.setText(output);
}
@Override
public boolean onOptionsItemSelected(MenuItem item){
int id = item.getItemId();
if (id== android.R.id.home){
this.finish();
}
return super.onOptionsItemSelected(item);
}
@Override
public void onDestroy() {
super.onDestroy();
Log.e("MyActivity", "on Destroy");
}
}
这是第二个活动的xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<TimePicker
android:id="@+id/time_picker"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:timePickerMode="clock" />
<Button
android:id="@+id/alarm_on"
android:layout_width="181dp"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentStart="true"
android:layout_marginBottom="66dp"
android:text="@string/AlarmOn" />
<Button
android:id="@+id/alarm_off"
android:layout_width="180dp"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:layout_marginBottom="55dp"
android:text="@string/AlarmOff" />
<TextView
android:id="@+id/update_text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_below="@+id/time_picker"
android:text="@string/SetAlarm"
android:textAlignment="center"
android:textSize="24sp" />
</RelativeLayout>
答案
首先,您没有在第二个活动布局中包含工具栏。您需要包含工具栏。这是我使用的解决方案,它没有问题。
在你的onCreate中添加它
initUI();
并在onCreate之后添加
@Override
public boolean onNavigateUp() {
onBackPressed();
return true;
}
public void initUI() {
toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
getSupportActionBar().setDisplayShowTitleEnabled(false);
toolbar.setNavigationOnClickListener(v -> onNavigateUp());
}
如果您有任何挑战,请告诉我。
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