我得到了一个用例，在这个用例中，我必须在我的项目中使用广播接收器，并且我知道这个类"LocalBroadcastManager"；已被弃用。
在谷歌文档中，他们建议使用Livedate，我尝试搜索一个很好的例子，但我没有看到任何适合我的情况。以下是我如何使用广播接收器：
MainActivity.java
private WeekFilterStatus weekFilterStatus;
//Inside onCreate
weekFilterStatus = new WeekFilterStatus();
LocalBroadcastManager.getInstance(getContext()).registerReceiver(weekFilterStatus, new IntentFilter("Week_filter"));
//outside onCreate
private class WeekFilterStatus extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
txtview.SetText("Week");
}
}
Dailog.java
go.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent= new Intent("Week_filter");
LocalBroadcastManager.getInstance(getContext()).sendBroadcast(intent);
dismiss();
}
});
这就是我在项目中使用的方式，我打开一个对话框，然后点击go，文本视图在主活动中得到更新。是的，我对此没有异议，因为它正在按预期工作，但我想知道用LiveData或任何其他方法实现这一点的其他方法。
如果你使用最新版本的Android studio并尝试调用LocalBroadcastManager类，你可能无法导入它，因为在我的情况下就是这样，所以这里有一个类，以防有人需要：
LocalBroadcastManager.java
/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.localbroadcastmanager.content;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.Uri;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import androidx.annotation.NonNull;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Set;
/**
* Helper to register for and send broadcasts of Intents to local objects
* within your process. This has a number of advantages over sending
* global broadcasts with {@link android.content.Context#sendBroadcast}:
* <ul>
* <li> You know that the data you are broadcasting won't leave your app, so
* don't need to worry about leaking private data.
* <li> It is not possible for other applications to send these broadcasts to
* your app, so you don't need to worry about having security holes they can
* exploit.
* <li> It is more efficient than sending a global broadcast through the
* system.
* </ul>
*/
public final class LocalBroadcastManager {
private static final class ReceiverRecord {
final IntentFilter filter;
final BroadcastReceiver receiver;
boolean broadcasting;
boolean dead;
ReceiverRecord(IntentFilter _filter, BroadcastReceiver _receiver) {
filter = _filter;
receiver = _receiver;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder(128);
builder.append("Receiver{");
builder.append(receiver);
builder.append(" filter=");
builder.append(filter);
if (dead) {
builder.append(" DEAD");
}
builder.append("}");
return builder.toString();
}
}
private static final class BroadcastRecord {
final Intent intent;
final ArrayList<ReceiverRecord> receivers;
BroadcastRecord(Intent _intent, ArrayList<ReceiverRecord> _receivers) {
intent = _intent;
receivers = _receivers;
}
}
private static final String TAG = "LocalBroadcastManager";
private static final boolean DEBUG = false;
private final Context mAppContext;
private final HashMap<BroadcastReceiver, ArrayList<ReceiverRecord>> mReceivers
= new HashMap<>();
private final HashMap<String, ArrayList<ReceiverRecord>> mActions = new HashMap<>();
private final ArrayList<BroadcastRecord> mPendingBroadcasts = new ArrayList<>();
static final int MSG_EXEC_PENDING_BROADCASTS = 1;
private final Handler mHandler;
private static final Object mLock = new Object();
private static LocalBroadcastManager mInstance;
@NonNull
public static LocalBroadcastManager getInstance(@NonNull Context context) {
synchronized (mLock) {
if (mInstance == null) {
mInstance = new LocalBroadcastManager(context.getApplicationContext());
}
return mInstance;
}
}
private LocalBroadcastManager(Context context) {
mAppContext = context;
mHandler = new Handler(context.getMainLooper()) {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_EXEC_PENDING_BROADCASTS:
executePendingBroadcasts();
break;
default:
super.handleMessage(msg);
}
}
};
}
/**
* Register a receive for any local broadcasts that match the given IntentFilter.
*
* @param receiver The BroadcastReceiver to handle the broadcast.
* @param filter Selects the Intent broadcasts to be received.
*
* @see #unregisterReceiver
*/
public void registerReceiver(@NonNull BroadcastReceiver receiver,
@NonNull IntentFilter filter) {
synchronized (mReceivers) {
ReceiverRecord entry = new ReceiverRecord(filter, receiver);
ArrayList<ReceiverRecord> filters = mReceivers.get(receiver);
if (filters == null) {
filters = new ArrayList<>(1);
mReceivers.put(receiver, filters);
}
filters.add(entry);
for (int i=0; i<filter.countActions(); i++) {
String action = filter.getAction(i);
ArrayList<ReceiverRecord> entries = mActions.get(action);
if (entries == null) {
entries = new ArrayList<ReceiverRecord>(1);
mActions.put(action, entries);
}
entries.add(entry);
}
}
}
/**
* Unregister a previously registered BroadcastReceiver. <em>All</em>
* filters that have been registered for this BroadcastReceiver will be
* removed.
*
* @param receiver The BroadcastReceiver to unregister.
*
* @see #registerReceiver
*/
public void unregisterReceiver(@NonNull BroadcastReceiver receiver) {
synchronized (mReceivers) {
final ArrayList<ReceiverRecord> filters = mReceivers.remove(receiver);
if (filters == null) {
return;
}
for (int i=filters.size()-1; i>=0; i--) {
final ReceiverRecord filter = filters.get(i);
filter.dead = true;
for (int j=0; j<filter.filter.countActions(); j++) {
final String action = filter.filter.getAction(j);
final ArrayList<ReceiverRecord> receivers = mActions.get(action);
if (receivers != null) {
for (int k=receivers.size()-1; k>=0; k--) {
final ReceiverRecord rec = receivers.get(k);
if (rec.receiver == receiver) {
rec.dead = true;
receivers.remove(k);
}
}
if (receivers.size() <= 0) {
mActions.remove(action);
}
}
}
}
}
}
/**
* Broadcast the given intent to all interested BroadcastReceivers. This
* call is asynchronous; it returns immediately, and you will continue
* executing while the receivers are run.
*
* @param intent The Intent to broadcast; all receivers matching this
* Intent will receive the broadcast.
*
* @see #registerReceiver
*
* @return Returns true if the intent has been scheduled for delivery to one or more
* broadcast receivers. (Note tha delivery may not ultimately take place if one of those
* receivers is unregistered before it is dispatched.)
*/
public boolean sendBroadcast(@NonNull Intent intent) {
synchronized (mReceivers) {
final String action = intent.getAction();
final String type = intent.resolveTypeIfNeeded(
mAppContext.getContentResolver());
final Uri data = intent.getData();
final String scheme = intent.getScheme();
final Set<String> categories = intent.getCategories();
final boolean debug = DEBUG ||
((intent.getFlags() & Intent.FLAG_DEBUG_LOG_RESOLUTION) != 0);
if (debug) Log.v(
TAG, "Resolving type " + type + " scheme " + scheme
+ " of intent " + intent);
ArrayList<ReceiverRecord> entries = mActions.get(intent.getAction());
if (entries != null) {
if (debug) Log.v(TAG, "Action list: " + entries);
ArrayList<ReceiverRecord> receivers = null;
for (int i=0; i<entries.size(); i++) {
ReceiverRecord receiver = entries.get(i);
if (debug) Log.v(TAG, "Matching against filter " + receiver.filter);
if (receiver.broadcasting) {
if (debug) {
Log.v(TAG, " Filter's target already added");
}
continue;
}
int match = receiver.filter.match(action, type, scheme, data,
categories, "LocalBroadcastManager");
if (match >= 0) {
if (debug) Log.v(TAG, " Filter matched! match=0x" +
Integer.toHexString(match));
if (receivers == null) {
receivers = new ArrayList<ReceiverRecord>();
}
receivers.add(receiver);
receiver.broadcasting = true;
} else {
if (debug) {
String reason;
switch (match) {
case IntentFilter.NO_MATCH_ACTION: reason = "action"; break;
case IntentFilter.NO_MATCH_CATEGORY: reason = "category"; break;
case IntentFilter.NO_MATCH_DATA: reason = "data"; break;
case IntentFilter.NO_MATCH_TYPE: reason = "type"; break;
default: reason = "unknown reason"; break;
}
Log.v(TAG, " Filter did not match: " + reason);
}
}
}
if (receivers != null) {
for (int i=0; i<receivers.size(); i++) {
receivers.get(i).broadcasting = false;
}
mPendingBroadcasts.add(new BroadcastRecord(intent, receivers));
if (!mHandler.hasMessages(MSG_EXEC_PENDING_BROADCASTS)) {
mHandler.sendEmptyMessage(MSG_EXEC_PENDING_BROADCASTS);
}
return true;
}
}
}
return false;
}
/**
* Like {@link #sendBroadcast(Intent)}, but if there are any receivers for
* the Intent this function will block and immediately dispatch them before
* returning.
*/
public void sendBroadcastSync(@NonNull Intent intent) {
if (sendBroadcast(intent)) {
executePendingBroadcasts();
}
}
@SuppressWarnings("WeakerAccess") /* synthetic access */
void executePendingBroadcasts() {
while (true) {
final BroadcastRecord[] brs;
synchronized (mReceivers) {
final int N = mPendingBroadcasts.size();
if (N <= 0) {
return;
}
brs = new BroadcastRecord[N];
mPendingBroadcasts.toArray(brs);
mPendingBroadcasts.clear();
}
for (int i=0; i<brs.length; i++) {
final BroadcastRecord br = brs[i];
final int nbr = br.receivers.size();
for (int j=0; j<nbr; j++) {
final ReceiverRecord rec = br.receivers.get(j);
if (!rec.dead) {
rec.receiver.onReceive(mAppContext, br.intent);
}
}
}
}
}
}
感谢您的帮助。谢谢
您可以通过创建如下所示的ViewModel类来使用LiveData
class MainViewModel : ViewModel() {
private val _text: MutableLiveData<String> = MutableLiveData()
val text: LiveData<String> get() = _text
fun setText(newText: String) {
_text.value = newText
}
}
在MainActivity中，您的代码将作为
class MainActivity : AppCompatActivity() {
private val viewModel by viewModels<MainViewModel>()
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val textview = findViewById<TextView>(R.id.text_view)
val go = findViewById<Button>(R.id.go)
viewModel.text.observe(this) {
textview.text = it
}
// todo
go.setOnClickListener {
viewModel.setText("Week")
}
}}