使用AppCompat v22.1.0时如何在super.onCreate之前设置ContentView？ [英] How to setContentView before super.onCreate while using AppCompat v22.1.0?

问题描述

嘿，我刚刚将我的应用升级到AppCompat v22.1.0，并遇到了此异常

Hey I've just upgraded my app to AppCompat v22.1.0 and got this exception

Caused by: java.lang.IllegalArgumentException: AppCompat does not support the current theme features
        at android.support.v7.app.AppCompatDelegateImplV7.ensureSubDecor(AppCompatDelegateImplV7.java:360) 
        at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:246) 
        at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:106) 

我找到了。此处 https://stackoverflow.com/a/29790071/2781359

问题仍然没有解决，因为我在 ConnectionWifiEditActivity 类中的super.onCreate之后调用setContentView。

Still the problem wasn't solved because I was calling the setContentView after super.onCreate, in the ConnectionWifiEditActivity Class.

当我更改此设置时，它引发 NullPointerException
我该如何解决？

When I changed this it throws NullPointerException How Can I Solve this?

Caused by: java.lang.NullPointerException
            at Client.Activity.connection.ConnectionEditActivity.onResume(ConnectionEditActivity.java:46)
            at Client.Activity.connection.ConnectionWifiEditActivity.onResume(ConnectionWifiEditActivity.java:81)

ConnectionWifiEditActivity

public class ConnectionWifiEditActivity extends ConnectionEditActivity implements OnClickListener
{
    private ConnectionWifi connection;
    private EditText host;
    private EditText port;
    Button scan;
    ListView lv;
    private Toolbar mToolbar;

    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.connectionwifiedit);
        lv = (ListView) findViewById(android.R.id.list);
        this.connection = (ConnectionWifi) connectionParam;
        mToolbar = (Toolbar) findViewById(R.id.toolbar_actionbar);
        setSupportActionBar(mToolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        this.host = (EditText) this.findViewById(R.id.host);
        this.port = (EditText) this.findViewById(R.id.port);
        SnackbarManager.show(
                Snackbar.with(getApplicationContext()) // context
                        .type(SnackbarType.MULTI_LINE) // Set is as a multi-line snackbar
                        .text(R.string.tip) // text to be displayed
                        .duration(Snackbar.SnackbarDuration.LENGTH_INDEFINITE)
                , this);
    }

    public void Save(View v){
        this.finish();
    }


    @Override
    public void onClick(View v)
    {

    }

    protected void onResume()
    {
        super.onResume();
        this.host.setText(this.connection.getHost());
        this.port.setText(Integer.toString(this.connection.getPort()));
    }

    protected void onPause()
    {
        super.onPause();

        this.connection.setHost(this.host.getText().toString());
        this.connection.setPort(Integer.parseInt(this.port.getText().toString()));
    }}

ConnectionEditActivity

public static Connection connectionParam;

    private Connection connection;

    private EditText name;
    private EditText password;

    public class ConnectionEditActivity extends AppCompatActivity implements OnClickListener
    {
        public static Connection connectionParam;

        private Connection connection;

        private Button save;

        private EditText name;
        private EditText password;

        protected void onCreate(Bundle savedInstanceState)
        {
            super.onCreate(savedInstanceState);
            this.connection = connectionParam;
            this.name = (EditText) this.findViewById(R.id.name);
            this.password = (EditText) this.findViewById(R.id.password);

        }

        protected void onResume()
        {
            super.onResume();
            this.name.setText(this.connection.getName());
            this.password.setText(this.connection.getPassword());
        }

        protected void onPause()
        {
            super.onPause();
            this.connection.setName(this.name.getText().toString());
            this.connection.setPassword(this.password.getText().toString());
        }

        public void onClick(View v)
        {
            if (v == this.save)
            {
                this.finish();
            }
        }
    }

连接

public abstract class Connection implements Comparable<Connection>, Serializable
{
    private static final long serialVersionUID = 1L;

    public static final int TYPE_COUNT = 2;

    public static final int WIFI = 0;
    public static final int BLUETOOTH = 1;

    private String name;
    private String password;

    public Connection()
    {
        this.name = "";
        this.password = RemoteItConnection.DEFAULT_PASSWORD;
    }

    public static Connection load(SharedPreferences preferences, ConnectionList list, int position)
    {
        Connection connection = null;
        int type = preferences.getInt("connection_" + position + "_type", -1);

        switch (type)
        {
            case WIFI:
                connection = ConnectionWifi.load(preferences, position);
                break;
            case BLUETOOTH:
                connection = ConnectionBluetooth.load(preferences, position);
                break;
        }

        connection.name = preferences.getString("connection_" + position + "_name", null);

        connection.password = preferences.getString("connection_" + position + "_password", null);

        return connection;
    }

    public void save(Editor editor, int position)
    {
        editor.putString("connection_" + position + "_name", this.name);

        editor.putString("connection_" + position + "_password", this.password);
    }

    public abstract RemoteItConnection connect(RemoteIt application) throws IOException;

    public abstract void edit(Context context);

    protected void edit(Context context, Intent intent)
    {
        ConnectionEditActivity.connectionParam = this;
        context.startActivity(intent);
    }

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public String getPassword()
    {
        return password;
    }

    public void setPassword(String password)
    {
        this.password = password;
    }

    public int compareTo(Connection c)
    {
        return this.name.compareTo(c.name);
    }
}

推荐答案

自要在super方法中获取一些ui元素，必须找到一种在超类中定义布局的方法。这是因为您按照其他答案中的说明获得了NPE。

Since you want to get some ui elements in the super method, you have to find a way to define the layout in the superclass. It is the reason because you are getting an NPE as described in the other answers.

您可以使用 setContentView（）使用一种方法返回要使用的布局。

You can use the setContentView() in the superclass, using a method to return the layout to use.

通过这种方式，您可以在子类中覆盖布局，从而覆盖方法。

In this way you can override the layout in the sub class, overriding the method.

例如，您可以使用类似 setContentView（getLayoutId（））的东西：

For example you can use something like setContentView(getLayoutId()):

public class ConnectionEditActivity extends AppCompatActivity {

    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);

        setContentView(getLayoutId());  //pay attention here...

        this.connection = connectionParam;
        this.name = (EditText) this.findViewById(R.id.name);
        this.password = (EditText) this.findViewById(R.id.password);
    }

    protected int getLayoutId(){
       //....
    }

}

您可以在其他活动中覆盖它，从而避免使用 setContentView

And you can override it in other activity, where you can avoid the setContentView method.

public class ConnectionWifiEditActivity extends ConnectionEditActivity{

   @Override
   protected int getLayoutId(){
       return R.layout.connectionwifiedit;
   }

    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        //setContentView();   //comment this line
        //..
    }

}

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