在移动设备上测试时没有错误的代码会崩溃

Question

我对 Android Studio 非常陌生，但我设法将 2 个活动放在一起，这些活动在单独的应用程序下运行良好，但加入后，当 MainActivity 调用 AddressActivity 使用 Intent 和 startActivity.

还有一个问题可能相关也可能不相关。安装应用程序时，没有请求任何权限。

这是我的代码：

AndroidManifest.xml

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COURSE_LOCATION" />
 <application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".AddressActivity"
        android:label="login">
    </activity>
</application>

MainActivity.class

package crproductionsptyltd.login;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import static crproductionsptyltd.login.R.id.driverid;
import static crproductionsptyltd.login.R.id.login;

public class MainActivity extends Activity {
    EditText driverid;
    Button btnOk;

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        // find View-elements
        btnOk = (Button) findViewById(login);
     //   btnOk.setOnClickListener(this)
        // create click listener
        View.OnClickListener oclBtnOk = new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // change text of the TextView (tvOut)
                btnOk.setText("Logging IN.....");

                Intent i = new Intent(MainActivity.this, AddressActivity.class);
                i.putExtra("driver_id", driverid.getText().toString());
                startActivity(i);
            };

        };
        // assign click listener to the OK button (btnOK)
        btnOk.setOnClickListener(oclBtnOk);
        //   startActivity(new Intent(MainActivity.this, AddressActivity.class));
       // Intent i = new Intent(MainActivity.this, NewActivity.class);//
        // startActivity(i);
    };
}

AddressActivity.class

package crproductionsptyltd.login;

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.Locale;
import android.app.Activity;
import android.content.Context;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;
import android.content.Intent;

public class AddressActivity extends Activity {
    /**
     * Called when the activity is first created.
     */
    String lat = "", lon = "";
    TextView tvView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_gps);
        tvView = (TextView) findViewById(R.id.tvView);
        Intent intent = getIntent();
        String driverid = intent.getStringExtra("driver_id");
        tvView.setText("Your Driver ID is: " + driverid);

        Button btnLocation = (Button) findViewById(R.id.btnLocation);
        btnLocation.setOnClickListener(new OnClickListener() {
            public void onClick(View arg0) {
                // Acquire a reference to the system Location Manager
                LocationManager locationManager = (LocationManager) AddressActivity.this.getSystemService(Context.LOCATION_SERVICE);
                // Define a listener that responds to location updates
                LocationListener locationListener = new LocationListener() {
                    public void onLocationChanged(Location location) {
                        // Called when a new location is found by the network location provider.
                        lat = Double.toString(location.getLatitude());
                        lon = Double.toString(location.getLongitude());
                        TextView tv = (TextView) findViewById(R.id.txtLoc);
                        tv.setText("Your Location is:" + lat + "--" + lon);
                    }

                    public void onStatusChanged(String provider, int status, Bundle extras) {
                    }

                    public void onProviderEnabled(String provider) {
                    }

                    public void onProviderDisabled(String provider) {
                    }
                };
                // Register the listener with the Location Manager to receive location updates

                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
            }
        });

        Button btnSend = (Button) findViewById(R.id.btnSend);
        btnSend.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                postData(lat, lon);
            }
        });

        Button btnAdd = (Button) findViewById(R.id.btnAddress);
        btnAdd.setOnClickListener(new OnClickListener() {
            public void onClick(View v) {
                TextView tv = (TextView) findViewById(R.id.txtAddress);
                tv.setText(GetAddress(lat, lon));
            }
        });
    }


    public void postData(String la, String lo) {
        //URL url = new URL("https://www.autoflora.net/driver/gps.php?Driver_ID=877&latlong=" + lat + "*" + lon);
        int TIMEOUT_VALUE = 15000;
            try{
                URL myUrl = new URL("https://www.autoflora.net/driver/gps.php?Driver_ID=877&latlong=" + lat + "*" + lon);
                URLConnection connection = myUrl.openConnection();
                connection.setConnectTimeout(TIMEOUT_VALUE);
                connection.connect();
            } catch (Exception e) {
            }
        }

    public String GetAddress(String lat, String lon)
    {
        Geocoder geocoder = new Geocoder(this, Locale.ENGLISH);
        String ret = "";
        try {
            List<Address> addresses = geocoder.getFromLocation(Double.parseDouble(lat), Double.parseDouble(lon), 1);
            if(addresses != null) {
                Address returnedAddress = addresses.get(0);
                StringBuilder strReturnedAddress = new StringBuilder("Address:\n");
                for(int i=0; i<returnedAddress.getMaxAddressLineIndex(); i++) {
                    strReturnedAddress.append(returnedAddress.getAddressLine(i)).append("\n");
                }
                ret = strReturnedAddress.toString();
            }
            else{
                ret = "No Address returned!";
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            ret = "Can't get Address!";
        }
        return ret;
    }
}

activity_login.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center_horizontal"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="crproductionsptyltd.login.LoginActivity">

    <!-- Login progress -->
    <ProgressBar
        android:id="@+id/login_progress"
        style="?android:attr/progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:visibility="gone" />

    <ScrollView
        android:id="@+id/login_form"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <LinearLayout
            android:id="@+id/email_login_form"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">

            <android.support.design.widget.TextInputLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content">

                <AutoCompleteTextView
                    android:id="@+id/driverid"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:hint="Driver ID"
                    android:inputType="textEmailAddress"
                    android:maxLines="1"
                    android:singleLine="true" />

            </android.support.design.widget.TextInputLayout>

            <android.support.design.widget.TextInputLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content">

            </android.support.design.widget.TextInputLayout>

            <Button
                android:id="@+id/login"
                style="?android:textAppearanceSmall"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_marginTop="16dp"
                android:text="Login"
                android:textStyle="bold"
                android:onClick="checkDriver" />

        </LinearLayout>
    </ScrollView>
</LinearLayout>

activity_gps.class

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/txtLoc"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView" />

    <TextView
        android:id="@+id/tvView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="20dp"
        android:textSize="20sp">
    </TextView>


    <Button
        android:id="@+id/btnLocation"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Get my Location" />

    <Button
        android:id="@+id/btnSend"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Send Location" />

    <Button
        android:id="@+id/btnAddress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Try Get Street Address" />

    <TextView
        android:id="@+id/txtAddress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Medium Text"
        android:textAppearance="?android:attr/textAppearanceMedium" />

</LinearLayout>

Answer 1

我想，使用android.support.design.widget.TextInputLayout 你应该使用这些依赖项

compile 'com.android.support:appcompat-v7:22.2.0'
compile 'com.android.support:design:22.2.0'

&还请指正

btnOk = (Button) findViewById(R.id.login);            //wrongly added
driverid = (EditText) findViewById(R.id.driverid);    // not added

Answer 2

根据您的代码，应用程序将在此处崩溃：i.putExtra("driver_id", driverid.getText().toString())，导致 NullPointerException。它崩溃是因为您没有在 onCreate 中对 EditText driverid; 进行初始化，因此，在未初始化的情况下使用时会抛出异常。

要解决此问题，您必须更新 onCreate 中的字段：

driverid = (EditText) findViewById(driverid);

在移动设备上测试时没有错误的代码会崩溃

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