Question

我是开发人员的新手，我开始按照本教程创建一个消息应用： http://sinch.github.io/android-messaging-tutorial/

添加第二个Activity（ListUsersActivity）及其布局文件后，每次运行应用程序时都会崩溃，不知道为什么会这样。

这是ListUsersActivity：

package com.sinch.messagingtutorialskeleton;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;

import com.example.messagingtutorialskeleton.R;
import com.parse.FindCallback;
import com.parse.ParseException;
import com.parse.ParseQuery;
import com.parse.ParseUser;

import java.util.ArrayList;
import java.util.List;


public class ListUsersActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstaceState){
    super.onCreate(savedInstaceState);
    setContentView(com.example.messagingtutorialskeleton.R.layout.activity_list_users);
        logoutButton = (Button) findViewById(R.id.logoutButton);
        logoutButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                ParseUser.logOut();
                Intent intent = new Intent(getApplicationContext(), LoginActivity.class);
                startActivity(intent);
            }
        });
        setConversationList();
    }

    private void setConversationList() {
        currentUserId = ParseUser.getCurrentUser().getObjectId();
        names = new ArrayList<String>();
        ParseQuery<ParseUser> query = ParseUser.getQuery();
        query.whereNotEqualTo("objectId", currentUserId);
        query.findInBackground(new FindCallback<ParseUser>() {
            public void done(List <ParseUser> userList, ParseException e) {
                if (e == null) {
                    for (int i=0; i<userList.size(); i++) {
                        names.add(userList.get(i).getUsername().toString());
                    }

                    usersListView = (ListView)findViewById(R.id.usersListView);
                    namesArrayAdapter =
                            new ArrayAdapter<String>(getApplicationContext(),
                                    R.layout.user_list_item, names);
                    usersListView.setAdapter(namesArrayAdapter);
                } else {
                    Toast.makeText(getApplicationContext(),
                            "Error loading user list",
                            Toast.LENGTH_LONG).show();
                }
            }
        });
        usersListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> a, View v, int i, long l) {
                Toast.makeText(getApplicationContext(),
                        "You clicked on user: " + i,
                        Toast.LENGTH_SHORT).show();
                //Look up user id and open conversation
            }
        });
    }

    private Button logoutButton;
    private String currentUserId;
    private ArrayAdapter<String> namesArrayAdapter;
    private ArrayList<String> names;
    private ListView usersListView;
}

现在的MainActivity（LoginActivity）：

package com.sinch.messagingtutorialskeleton;

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 android.widget.Toast;

import com.example.messagingtutorialskeleton.R;
import com.parse.LogInCallback;
import com.parse.Parse;
import com.parse.ParseException;
import com.parse.ParseUser;
import com.parse.SignUpCallback;


public class LoginActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ParseUser currentUser = ParseUser.getCurrentUser();
    if (currentUser != null) {
        //start new activity
        Intent intent = new Intent(getApplicationContext(), ListUsersActivity.class);
        startActivity(intent);
    }
    setContentView(com.example.messagingtutorialskeleton.R.layout.activity_login);
    Parse.initialize(this, "uUv5HM8nqz9gVQBDWaw1bDLxbD3SFQPQtvDESJG1", "BHVp4MQbiOODY3yGOrM7pgaZ0xTbCPI1v6dfRU6C");
    loginButton = (Button) findViewById(R.id.loginButton);
    signUpButton = (Button) findViewById(R.id.signupButton);
    usernameField = (EditText) findViewById(R.id.loginUsername);
    passwordField = (EditText) findViewById(R.id.loginPassword);


    loginButton.setOnClickListener(new View.OnClickListener() {



        @Override
        public void onClick(View view) {
            Toast.makeText(getApplicationContext(), "Login",
                    Toast.LENGTH_SHORT).show();

            username = usernameField.getText().toString();
            password = passwordField.getText().toString();

            ParseUser.logInInBackground(username, password, new LogInCallback() {
                public void done(ParseUser user, ParseException e) {
                    if (user != null) {
                        //start new activity
                        Intent intent = new Intent(getApplicationContext(), ListUsersActivity.class);
                        startActivity(intent);
                    } else {
                        Toast.makeText(getApplicationContext(),
                                "Wrong username/password combo",
                                Toast.LENGTH_LONG).show();
                    }
                }
            });
        }

    });

    signUpButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Toast.makeText(getApplicationContext(), "Sign Up",
                    Toast.LENGTH_SHORT).show();

            username = usernameField.getText().toString();
            password = passwordField.getText().toString();

            ParseUser user = new ParseUser();
            user.setUsername(username);
            user.setPassword(password);

            user.signUpInBackground(new SignUpCallback() {
                public void done(ParseException e) {
                    if (e == null) {
                        //start new activity
                        Intent intent = new Intent(getApplicationContext(), ListUsersActivity.class);
                        startActivity(intent);
                    } else {
                        Toast.makeText(getApplicationContext(),
                                "There was an error signing up."
                                , Toast.LENGTH_LONG).show();
                    }
                }
            });
        }
    });
}

private Button signUpButton;
private Button loginButton;
private EditText usernameField;
private EditText passwordField;
private String username;
private String password;

}

AndroidManifest.xml：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.messagingtutorialskeleton" >

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.Light.NoTitleBar"> >
    <activity
        android:name="com.sinch.messagingtutorialskeleton.LoginActivity"
        android:screenOrientation="portrait" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name="com.sinch.messagingtutorialskeleton.ListUsersActivity"
        android:screenOrientation="portrait">
    </activity>
</application>

</manifest>

activity_login.xml（LoginActivity的布局文件）：

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="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.sinch.messagingtutorial.app.LoginActivity">

<LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_centerVertical="true"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="40dp"
        android:text="@string/username"
        android:id="@+id/loginUsernameText"
        android:layout_gravity="center_horizontal"
        android:textColor="@color/sinch_purple"
        android:textSize="20sp"/>
    <EditText
        android:id="@+id/loginUsername"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:inputType="text"
        android:textSize="32sp"
        android:padding="10dp"
        android:textColor="@color/sinch_purple"
        android:background="@drawable/inputbox"
        android:layout_marginLeft="30dp"
        android:layout_marginRight="30dp">
        <requestFocus/>
    </EditText>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="40dp"
        android:text="@string/password"
        android:id="@+id/loginPasswordText"
        android:layout_gravity="center_horizontal"
        android:textColor="@color/sinch_purple"
        android:textSize="20sp"/>
    <EditText
        android:id="@+id/loginPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginBottom="40dp"
        android:inputType="textPassword"
        android:textSize="32sp"
        android:padding="10dp"
        android:textColor="@color/sinch_purple"
        android:background="@drawable/inputbox"
        android:layout_marginLeft="30dp"
        android:layout_marginRight="30dp">
    </EditText>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_marginBottom="40dp"
        android:layout_gravity="center">

        <Button
            android:id="@+id/loginButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@drawable/button_login"/>

        <Button
            android:id="@+id/signupButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@drawable/button_signup"/>
    </LinearLayout>
</LinearLayout>
</RelativeLayout>

activity_list_users.xml（UserListActivity布局）：

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
tools:context="com.sinch.messagingtutorial.app.ListUsersActivity"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >

<Button
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/logout"
    android:id="@+id/logoutButton"
    android:gravity="center_vertical|center_horizontal"
    android:layout_gravity="center_horizontal"
    android:background="@color/dark_gray"
    android:textSize="24sp"
    android:padding="15dp"
    android:textColor="@color/sinch_purple" />

<ListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp"
    android:background="@color/off_white"
    android:id="@+id/usersListView">
 </ListView>

 </LinearLayout>

将logcat放在这里时出错，所以我把它上传到了pastebin： http://pastebin.com/nzg2YbfZ

Answer 1

尝试移动：

setContentView(com.example.messagingtutorialskeleton.R.layout.activity_login);
Parse.initialize(this, "uUv5HM8nqz9gVQBDWaw1bDLxbD3SFQPQtvDESJG1","BHVp4MQbiOODY3yGOrM7pgaZ0xTbCPI1v6dfRU6C");
loginButton = (Button) findViewById(R.id.loginButton);
signUpButton = (Button) findViewById(R.id.signupButton);
usernameField = (EditText) findViewById(R.id.loginUsername);
passwordField = (EditText) findViewById(R.id.loginPassword);

之前：

if (currentUser != null) {
    //start new activity
    Intent intent = new Intent(getApplicationContext(), ListUsersActivity.class);
    startActivity(intent);
}

后：

ParseUser currentUser = ParseUser.getCurrentUser();

我只是猜测，当你开始活动时，它就会停在那里，并且没有得到剩下的东西，包括 Parse.initialize（）;如果它不起作用，那么抱歉！请不要downvote！

修改

正如弗雷德里克在下面所说的，它引用了那条线，在它调用活动之前是可疑的，并且它表示在该行的位置应该有Parse.initialize（），或者在你开始之前新活动。

Answer 2

检查您发布的logcat。

Caused by: java.lang.RuntimeException: You must call Parse.initialize(context, oauthKey, oauthSecret) before using the Parse library.
        at com.parse.ParseUser.checkApplicationContext(ParseUser.java:1104)
        at com.parse.ParseUser.getCurrentUser(ParseUser.java:904)
        at com.sinch.messagingtutorialskeleton.LoginActivity.onCreate(LoginActivity.java:24)

如果您检查代码引用此行（LoginActivity：24）...

ParseUser currentUser = ParseUser.getCurrentUser();

我没有使用过该库，但很明显你必须调用

Parse.initialize(this, "**parse key**","**parse key**");

在 ParseUser.getCurrentUser（）;

之前

**对于ListUserActivity中的第二次崩溃**

将行拆分为两行，这样就可以检查＆＃34; getCurrentUser（）＆＃34;方法失败了：

...
// Line 65
ParseUser mCurrentUser = ParseUser.getCurrentUser(); // Breakpoint here in Android Studio and go step by step for checking return value
currentUserId = mCurrentUser.getObjectId();
...

有关调试的建议......

应用程序在添加新活动后崩溃

2 个答案: