Question

我是Android新手，我希望点击按钮获取current location。我关注this documentation作为教程。除showLocation()外，所有功能都正常工作。如果我只是在这个函数中写一个toast消息，那么它工作正常但是当我添加代码来获取位置时，我在app ShanTest app unfortunately stopped中出错。

我尝试评论下面的代码，并用TOAST消息替换它，然后它工作正常。出现错误的代码如下： -

mFusedLocationClient.getLastLocation()
                    .addOnSuccessListener(this, new OnSuccessListener<Location>() {
                        @Override
                        public void onSuccess(Location location) {
                            // Got last known location. In some rare situations this can be null.
                            if (location != null) {
                                // Logic to handle location object
                                onLocationChanged(location);
                            }
                            else {
                                Toast.makeText(getApplicationContext(), "Oops", Toast.LENGTH_SHORT).show();
                            }
                        }
                    });

SDK Manager

的build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.3"
    dataBinding.enabled = true
    defaultConfig {
        applicationId "com.example.borntoflirt.design1"
        minSdkVersion 21
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.3.1'
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    compile 'com.google.android.gms:play-services-location:11.0.4'
    testCompile 'junit:junit:4.12'
}

events.java

     package com.example.borntoflirt.design1;

import android.Manifest;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.Build;
import android.media.MediaPlayer.OnCompletionListener;
import android.support.annotation.NonNull;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.animation.BounceInterpolator;
import android.widget.Button;
import android.widget.Toast;

import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraManager;
import android.media.MediaPlayer;

import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.tasks.OnSuccessListener;

import java.util.Calendar;
import java.text.SimpleDateFormat;

public class events extends AppCompatActivity {

    private CameraManager mCameraManager;
    private String mCameraId;
    private Button mTorchOnOffButton;
    private Boolean isTorchOn;
    private Boolean isFlashAvailable;

    private FusedLocationProviderClient mFusedLocationClient;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_events);

        mTorchOnOffButton = (Button) findViewById(R.id.mTorchOnOffButton);
        isFlashAvailable = getApplicationContext().getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
        isTorchOn = false;

        mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        try {
            mCameraId = mCameraManager.getCameraIdList()[0];
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }

        mTorchOnOffButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    if (isFlashAvailable) {
                        if (isTorchOn) {
                            turnOffFlashLight();
                            isTorchOn = false;
                        } else {
                            turnOnFlashLight();
                            isTorchOn = true;
                        }
                    }
                    else {
                        Toast.makeText(getApplicationContext(), "Flash is not supported", Toast.LENGTH_SHORT).show();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });

        mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);
    }

    public void turnOnFlashLight() {
        try {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                mCameraManager.setTorchMode(mCameraId, true);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public void turnOffFlashLight() {
        try {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                mCameraManager.setTorchMode(mCameraId, false);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void showToast(View v) {
        Context context = getApplicationContext();  // OR getBaseContext()
        CharSequence text = "Hello Toast";
        int duration = Toast.LENGTH_SHORT;

        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
    }

    public void showAlert(View v) {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("Write your message here.");
        builder.setCancelable(false);

        builder.setPositiveButton(
                "ok",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        // Do Task
                        Toast.makeText(getApplicationContext(),
                                "You clicked on OK", Toast.LENGTH_SHORT)
                                .show();
                    }
                });

        builder.setNegativeButton(
                "Cancel",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();
                    }
                });

        AlertDialog alert = builder.create();
        alert.show();
    }

    public void showDate(View v) {
        Calendar calendar = Calendar.getInstance();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd-mm-yyyy HH:mm:ss");
        String currentDateTime = simpleDateFormat.format(calendar.getTime());
        Toast.makeText(getApplicationContext(), currentDateTime, Toast.LENGTH_LONG).show();
    }

    public void showLocation() {
        int permissionCheck = ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION);
        if( permissionCheck != PackageManager.PERMISSION_GRANTED ) {
            //Toast.makeText(getApplicationContext(), "Granted", Toast.LENGTH_SHORT).show();
            mFusedLocationClient.getLastLocation()
                    .addOnSuccessListener(this, new OnSuccessListener<Location>() {
                        @Override
                        public void onSuccess(Location location) {
                            // Got last known location. In some rare situations this can be null.
                            if (location != null) {
                                // Logic to handle location object
                                onLocationChanged(location);
                            }
                            else {
                                Toast.makeText(getApplicationContext(), "Oops", Toast.LENGTH_SHORT).show();
                            }
                        }
                    });
        }
        else {
            Toast.makeText(getApplicationContext(), "Permission Not Granted", Toast.LENGTH_SHORT).show();
        }
    }

    public void onLocationChanged(Location location) {
        // New location has now been determined
        String msg = "Updated Location: " +
                Double.toString(location.getLatitude()) + "," +
                Double.toString(location.getLongitude());
        Toast.makeText(this, msg, Toast.LENGTH_SHORT).show();
    }

}

Answer 1

假设在清单中设置了所有权限，并且依赖性良好。

mFusedLocationClient似乎没有在代码中的任何位置初始化。根据{{3}}

在onCreate中执行此操作

mFusedLocationClient = LocationServices.getFusedLocationProviderClient(this);

不幸停止了按钮点击应用中的Android获取位置

1 个答案: