android活动线程settext错误

Question

02-27 22:53:13.047: E/AndroidRuntime(11744): FATAL EXCEPTION: main
02-27 22:53:13.047: E/AndroidRuntime(11744): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.itcuties.android.reader/com.itcuties.android.reader.ItemDescriptionActivity}: java.lang.NullPointerException
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.os.Handler.dispatchMessage(Handler.java:99)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.os.Looper.loop(Looper.java:137)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.app.ActivityThread.main(ActivityThread.java:5041)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at java.lang.reflect.Method.invokeNative(Native Method)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at java.lang.reflect.Method.invoke(Method.java:511)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at dalvik.system.NativeStart.main(Native Method)
02-27 22:53:13.047: E/AndroidRuntime(11744): Caused by: java.lang.NullPointerException
02-27 22:53:13.047: E/AndroidRuntime(11744):    at com.itcuties.android.reader.ItemDescriptionActivity.onCreate(ItemDescriptionActivity.java:18)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.app.Activity.performCreate(Activity.java:5104)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-27 22:53:13.047: E/AndroidRuntime(11744):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
02-27 22:53:13.047: E/AndroidRuntime(11744):    ... 11 more

还有ItemDescriptionActivity.java

package com.itcuties.android.reader;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
import com.itcuties.android.reader.R;

public class ItemDescriptionActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.item);

        Bundle bundle = getIntent().getExtras();
        String item_description = bundle.getString("description");

        TextView desc = (TextView) findViewById(R.layout.item);
        desc.setText(item_description);
    }
}

应用正在获取 rss 数据，在列表视图中显示标题。我正在尝试在点击时添加显示描述，但点击时应用程序崩溃。什么会导致这些错误？

Answer 1

您需要将id 传递给findViewById()，也许您打算使用findViewById(R.id.item);。如果您仍然遇到同样的 LogCat 错误，请确保布局 item.xml 实际上有一个 TextView，其 id 为：@+id/item。

此外，并非每个 Activity 都以 Intent 启动，并且并非每个 Intent 都有额外内容，在使用它们之前，您应该确保这些值都不是 null。

---

添加另一个 RSS 值

让我们把链接和描述一起传递：

public void onItemClick(AdapterView<?> parent, View view, int pos, long id) {   
    Intent intent = new Intent(activity, ItemDescriptionActivity.class);

    RSSItem item = listItems.get(pos);
    intent.putExtra("description", item.getDescription());
    intent.putExtra("link", item.getLink());
    activity.startActivity(intent);
}   

接下来我们将在ItemDescriptionActivity 中创建一个新的类变量：

String item_link;

最后设置按钮打开网页中的链接：

item_link = bundle.getString("link");
Button link = (Button) findViewById(R.id.button1);
link.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View view) {
        Intent browse = new Intent(Intent.ACTION_VIEW, Uri.parse(item_link));
        startActivity(browse);
    }
}