Question

这是我的应用程序的编码，我正在使用Eclipse。

DisplayMessageActivity.java

package com.example.myfirstapp;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;

@SuppressLint("NewApi") public class DisplayMessageActivity extends Activity 
{
    @SuppressLint("NewApi") @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_message);
        // Show the Up button in the action bar.
        getActionBar().setDisplayHomeAsUpEnabled(true);
        //Get the message from the intent
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

        //Create the text view
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        //Set the text view
        setContentView(textView);
    }

//  OKAY TO REMOVE
    @Override
    public boolean onCreateOptionsMenu(Menu menu) 
    {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_display_message, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) 
    {
        switch (item.getItemId()) 
        {
        case android.R.id.home:
            // This ID represents the Home or Up button. In the case of this
            // activity, the Up button is shown. Use NavUtils to allow users
            // to navigate up one level in the application structure. For
            // more details, see the Navigation pattern on Android Design:
            //
            // http://developer.android.com/design/patterns/navigation.html#up-vs-back
            //
            NavUtils.navigateUpFromSameTask(this);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

}

<小时/> MyFirstAppManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.myfirstapp"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" android:debuggable="true">
        <activity
            android:name="com.example.myfirstapp.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.example.myfirstapp.DisplayMessageActivity"
            android:label="@string/title_activity_display_message"
            android:parentActivityName="com.example.myfirstapp.MainActivity" >
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.example.myfirstapp.MainActivity" />
        </activity>
    </application>

</manifest>

<小时/> MainActivity.java

package com.example.myfirstapp;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends Activity 
{
    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    /** Called when the user clicks the Send button */
    public  void sendMessage (View view)
    {
        // Do something in response to button
        Intent intent = new Intent(this, DisplayMessageActivity.class);
        EditText editText = (EditText) findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
    }
}

如果您需要更多信息或调试结果，请告诉我们。我正在关注位于here的Android开发人员教程。

Answer 1

如果没有LogCat，我可以解决您的代码中的一个问题。 @SuppressLint("NewApi")。 Lint很重要 - 你的目标API是8. Froyo和Gingerbread没有Action Bar。

现在，在DisplayMessageActivity中创建一个这样的方法：

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    private void setupActionBar() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            // Show the Up button in the action bar.
            getActionBar().setDisplayHomeAsUpEnabled(true);
        }
    }

现在从DisplayMessageActivity

中的代码中取出这一行

getActionBar().setDisplayHomeAsUpEnabled(true);

并将其替换为

setupActionBar();

Android会检查API版本，如果它低于HoneyComb，则不会调用Gingerbread上不存在的getActionBar()方法。

我如何在eclipse中解决这个致命的异常？

1 个答案: