在 ActionBar 中使用 SearchView

Question

我正在尝试运行一个简单的代码，当用户单击Search action 时显示SearchView。

当我运行 application 时，它以 FATAL EXCEPTION 关闭。

我的代码

MainActivity.java

package luizugliano.com.br.customactionbar;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.SearchView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);

    MenuItem item = menu.findItem(R.id.action_search);
    SearchView searchView = (SearchView) item.getActionView();
    searchView.setOnQueryTextListener(onSearch());
    return true;
}

private SearchView.OnQueryTextListener onSearch() {
    return new SearchView.OnQueryTextListener(){
        @Override
        public boolean onQueryTextSubmit(String query) {
            // Usuário fez a busca
            toastMessage("Buscar o texto: " + query);
            return false;
        }
        @Override
        public boolean onQueryTextChange(String newText) {
            // Mudou o texto digitado
            return false;
        }
    };
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_search) {
        toastMessage("Search!");
        return true;
    } else if (id == R.id.action_refresh){
        toastMessage("Refresh!");
        return true;
    } else if (id == R.id.action_settings){
        toastMessage("Settings!");
        return true;
    }

    return super.onOptionsItemSelected(item);
}

private void toastMessage(String message){
    Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
}
}

menu_main.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools" tools:context=".MainActivity">
<item android:id="@+id/action_search" android:title="@string/action_search"
    android:orderInCategory="100" android:icon="@drawable/ic_action_search" app:showAsAction="always"
    android:actionViewClass="android.widget.SearchView"/>
<item android:id="@+id/action_refresh" android:title="@string/action_refresh"
    android:orderInCategory="100" android:icon="@drawable/ic_action_refresh" app:showAsAction="always" />
<item android:id="@+id/action_settings" android:title="@string/action_settings"
    android:orderInCategory="100" app:showAsAction="never" />

logcat 信息

10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar D/AndroidRuntime：关闭 VM 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 致命异常: main 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 进程: luizugliano.com.br.customactionbar, PID: 806 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: java.lang.NullPointerException: 尝试调用虚拟方法 'void android.widget.SearchView.setOnQueryTextListener(android.widget.SearchView$ OnQueryTextListener)' 在空对象引用上 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 luizugliano.com.br.customactionbar.MainActivity.onCreateOptionsMenu(MainActivity.java:29) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.app.Activity.onCreatePanelMenu(Activity.java:2846) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.support.v4.app.FragmentActivity.onCreatePanelMenu(FragmentActivity.java:298) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.support.v7.internal.view.WindowCallbackWrapper.onCreatePanelMenu(WindowCallbackWrapper.java:85) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.support.v7.app.AppCompatDelegateImplBase$AppCompatWindowCallbackBase.onCreatePanelMenu(AppCompatDelegateImplBase.java:243) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.support.v7.internal.view.WindowCallbackWrapper.onCreatePanelMenu(WindowCallbackWrapper.java:85) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.support.v7.internal.app.ToolbarActionBar.populateOptionsMenu(ToolbarActionBar.java:448) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.support.v7.internal.app.ToolbarActionBar$1.run(ToolbarActionBar.java:65) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.os.Handler.handleCallback(Handler.java:739) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.os.Handler.dispatchMessage(Handler.java:95) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.os.Looper.loop(Looper.java:148) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 android.app.ActivityThread.main(ActivityThread.java:5417) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime：在 java.lang.reflect.Method.invoke（本机方法） 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 10-20 00:30:21.327 806-806/luizugliano.com.br.customactionbar E/AndroidRuntime: 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 10-20 00:30:21.686 806-820/luizugliano.com.br.customactionbar I/art：后台部分并发标记扫描 GC 释放 205(8KB) AllocSpace 对象，0(0B) LOS 对象，40% 免费，5MB/ 8MB，暂停 41.133ms 共 119.832ms 10-20 00:30:35.570 806-806/? I/Process：发送信号。 PID：806 SIG：9

Answer 1

错误消息 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.SearchView.setOnQueryTextListener(android.widget.SearchView$OnQueryTextListener)' on a null object reference 意味着正在尝试在 null searchView 上调用 setOnQueryTextListener。

在您的 menu_main.xml 中，更改

android:actionViewClass="android.widget.SearchView"

到

app:actionViewClass="android.support.v7.widget.SearchView"

在你的 MainActivity.java 中，改变

SearchView searchView = (SearchView) item.getActionView();

与

SearchView searchView = (SearchView) MenuItemCompat.getActionView(menu.findItem(R.id.action_search)); 

Answer 2

您需要与 Java 和 XML 代码库中的搜索视图访问支持库的使用保持一致。不正确使用它会导致 NPE。