我第一次尝试使用 Google 的 Nearby Messages API。我从 GitHub 下载了一些源代码，并尝试使用 Android Studio 对其进行编译。有一个 Android Studio 无法解析的导入：
import com.google.android.gms.nearby.messages.SubscribeOptions;
我的 Gradle 文件定义了以下依赖项：
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:23.2.0'
compile 'com.google.android.gms:play-services:7.8.0'
compile 'com.google.android.gms:play-services-nearby:7.8.0'
这就是Activity我使用上述库的地方：
package com.example.android.nearbybeacons;
import android.Manifest;
import android.app.PendingIntent;
import android.content.Intent;
import android.content.IntentSender;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.common.api.ResultCallback;
import com.google.android.gms.common.api.Status;
import com.google.android.gms.nearby.Nearby;
import com.google.android.gms.nearby.messages.Message;
import com.google.android.gms.nearby.messages.MessageListener;
import com.google.android.gms.nearby.messages.Strategy;
import com.google.android.gms.nearby.messages.SubscribeOptions;
public class MainActivity extends AppCompatActivity implements
AdapterView.OnItemClickListener,
GoogleApiClient.ConnectionCallbacks,
GoogleApiClient.OnConnectionFailedListener {
private static final String TAG =
MainActivity.class.getSimpleName();
private static final int REQUEST_RESOLVE_ERROR = 100;
private static final int REQUEST_PERMISSION = 42;
private GoogleApiClient mGoogleApiClient;
private ArrayAdapter<OfferBeacon> mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView list = (ListView) findViewById(R.id.list);
mAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1);
list.setAdapter(mAdapter);
list.setOnItemClickListener(this);
//Construct a connection to Play Services
mGoogleApiClient = new GoogleApiClient.Builder(this)
.addConnectionCallbacks(this)
.addOnConnectionFailedListener(this)
.addApi(Nearby.MESSAGES_API)
.build();
//When launching from a notification link
if (BeaconService.ACTION_DISMISS.equals(getIntent().getAction())) {
//Fire a clear action to the service
Intent intent = new Intent(this, BeaconService.class);
intent.setAction(BeaconService.ACTION_DISMISS);
startService(intent);
}
}
@Override
protected void onStart() {
super.onStart();
//Initiate connection to Play Services
mGoogleApiClient.connect();
//The location permission is required on API 23+ to obtain BLE scan results
int result = ActivityCompat
.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION);
if (result != PackageManager.PERMISSION_GRANTED) {
//Ask for the location permission
ActivityCompat.requestPermissions(this,
new String[]{Manifest.permission.ACCESS_COARSE_LOCATION},
REQUEST_PERMISSION);
}
}
@Override
protected void onStop() {
super.onStop();
//Tear down Play Services connection
if (mGoogleApiClient.isConnected()) {
Log.d(TAG, "Un-subscribing…");
Nearby.Messages.unsubscribe(
mGoogleApiClient,
mMessageListener);
mAdapter.clear();
mGoogleApiClient.disconnect();
}
}
// This is called in response to a button tap in the system permissions dialog.
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == REQUEST_RESOLVE_ERROR) {
if (resultCode == RESULT_OK) {
// Permission granted or error resolved successfully then we proceed
// with publish and subscribe..
subscribe();
} else {
// This may mean that user had rejected to grant nearby permission.
showToast("Failed to resolve error with code " + resultCode);
}
}
if (requestCode == REQUEST_PERMISSION) {
if (resultCode != RESULT_OK) {
showToast("We need location permission to get scan results!");
finish();
}
}
}
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
OfferBeacon item = mAdapter.getItem(position);
showToast(item.offer);
}
/* Nearby Messages Callbacks */
//NOTE: These callbacks are NOT triggered on the main thread!
private MessageListener mMessageListener = new MessageListener() {
// Called each time a new message is discovered nearby.
@Override
public void onFound(Message message) {
Log.i(TAG, "Found message: " + message);
final OfferBeacon beacon = new OfferBeacon(message);
runOnUiThread(new Runnable() {
@Override
public void run() {
mAdapter.add(beacon);
}
});
}
// Called when the publisher (beacon) is no longer nearby.
@Override
public void onLost(Message message) {
Log.i(TAG, "Lost message: " + message);
final OfferBeacon beacon = new OfferBeacon(message);
runOnUiThread(new Runnable() {
@Override
public void run() {
mAdapter.remove(beacon);
}
});
}
};
/* API Client Callbacks */
@Override
public void onConnected(Bundle bundle) {
//Once connected, we have to check that the user has opted in
Runnable runOnSuccess = new Runnable() {
@Override
public void run() {
//Subscribe once user permission is verified
subscribe();
}
};
ResultCallback<Status> callback =
new ErrorCheckingCallback(runOnSuccess);
Nearby.Messages.getPermissionStatus(mGoogleApiClient)
.setResultCallback(callback);
}
@Override
public void onConnectionSuspended(int i) {
Log.d(TAG, "OnConnectionSuspended");
}
@Override
public void onConnectionFailed(ConnectionResult connectionResult) {
Log.w(TAG, "OnConnectionFailed");
}
private void subscribe() {
Log.d(TAG, "Subscribing…");
SubscribeOptions options = new SubscribeOptions.Builder()
.setStrategy(Strategy.BLE_ONLY)
.build();
//Active subscription for foreground messages
Nearby.Messages.subscribe(mGoogleApiClient,
mMessageListener, options);
//Passive subscription for background messages
Intent serviceIntent = new Intent(this, BeaconService.class);
PendingIntent trigger = PendingIntent.getService(this, 0,
serviceIntent, PendingIntent.FLAG_UPDATE_CURRENT);
ResultCallback<Status> callback = new BackgroundRegisterCallback();
Nearby.Messages.subscribe(mGoogleApiClient, trigger, options)
.setResultCallback(callback);
}
private class BackgroundRegisterCallback implements ResultCallback<Status> {
@Override
public void onResult(@NonNull Status status) {
//Validate if we were able to register for background scans
if (status.isSuccess()) {
Log.d(TAG, "Background Register Success!");
} else {
Log.w(TAG, "Background Register Error ("
+ status.getStatusCode() + "): "
+ status.getStatusMessage());
}
}
}
//ResultCallback triggered when to handle Nearby permissions check
private class ErrorCheckingCallback implements ResultCallback<Status> {
private final Runnable runOnSuccess;
private ErrorCheckingCallback(@Nullable Runnable runOnSuccess) {
this.runOnSuccess = runOnSuccess;
}
@Override
public void onResult(@NonNull Status status) {
if (status.isSuccess()) {
Log.i(TAG, "Permission status succeeded.");
if (runOnSuccess != null) {
runOnSuccess.run();
}
} else {
// Currently, the only resolvable error is that the device is not opted
// in to Nearby. Starting the resolution displays an opt-in dialog.
if (status.hasResolution()) {
try {
status.startResolutionForResult(MainActivity.this,
REQUEST_RESOLVE_ERROR);
} catch (IntentSender.SendIntentException e) {
showToastAndLog(Log.ERROR, "Request failed with exception: " + e);
}
} else {
showToastAndLog(Log.ERROR, "Request failed with : " + status);
}
}
}
}
private void showToast(String text) {
Toast.makeText(this, text, Toast.LENGTH_SHORT).show();
}
private void showToastAndLog(int logLevel, String message) {
Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
Log.println(logLevel, TAG, message);
}
}
谁能告诉我我做错了什么？