Question

我是学习Android开发的新手，我正在关注this tutorial来创建一个小应用程序。我只是改变了一些代码。当我点击发送按钮时，我得到一个提示“不幸的是，我的第一个应用已经停止了。”有人可以告诉我无论如何。

我替换了教程中给出的代码（此处显示为第二类代码中的块注释），并替换为包含 * 的注释的代码。

第一项活动： -

package com.practice.firstapp1;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;
import com.practice.firstapp1.R;

public class MainActivity extends Activity {

    public final static String EXTRA_MESSAGE= "com.practice.fristapp1.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.main, menu);
        return true;
    }

    /** Called when the user clicks the Send button */
    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        Intent intent = new Intent(this, DisplayMessageActivity.class);
        EditText editText = (EditText) findViewById(R.id.id1);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
    }

}

第一次活动的布局： -

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">
    <EditText android:id="@+id/id1"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message" />
    <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/button_send"
    android:onClick="sendMessage" />
</LinearLayout>

第二次活动的代码： -

    package com.practice.firstapp1;

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

    public class DisplayMessageActivity extends Activity {

        @SuppressLint("NewApi")
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_display_message);

            // Make sure we're running on Honeycomb or higher to use ActionBar APIs
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
                // Show the Up button in the action bar.
                getActionBar().setDisplayHomeAsUpEnabled(true);
            }

            //Get the intent which invoked this activity and read its extra's data into the string named message.
            Intent intent = getIntent();
            String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

            TextView textView = (TextView) findViewById(R.id.text_view_2); //************
            textView.setText(message);//***********

            setContentView(textView);//***********
//The above three statements along with statements from its layout (which have been given *s in comments have been placed instead of the statements in the following block comment. Because I wanted to create the TextView in layout.xml and handle its work in code.

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

    // Set the text view as the activity layout
    setContentView(textView);
*/

        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            switch (item.getItemId()) {
            case android.R.id.home:
                NavUtils.navigateUpFromSameTask(this);
                return true;
            }
            return super.onOptionsItemSelected(item);
        }
    }

第二次活动的布局： -

<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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".DisplayMessageActivity" >

    <TextView    <!--//*********************************-->
        android:id="@+id/text_view_2"    <!--//***********************-->
        android:layout_width="wrap_content"    <!--//**********************-->
        android:layout_height="wrap_content"    <!--//**************-->
        android:textSize="40sp" />    <!--//**************************-->


</RelativeLayout>

ANDROID MANIFEST FILE： -

    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.practice.firstapp1"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.practice.firstapp1.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.practice.firstapp1.DisplayMessageActivity"
            android:label="@string/title_activity_display_message"
            android:parentActivityName="com.practice.firstapp1.MainActivity" >
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.practice.firstapp1.MainActivity" />
        </activity>
    </application>

</manifest>

Answer 1

来自您的评论

I havn't done anything in the manifest file. I think it is done automatically when we are using eclipse.

是的，如果您创建新的Android活动，eclipse会将活动添加到清单。

你的清单看起来很好。删除以下行

编辑1：

setContentView(textView);

activity_display_message.xml已经有了textview，您可以在代码中初始化textView并设置文本。 TextView已经有了父级。

无需setContentView(textView)

为什么我的简单应用程序会停止

1 个答案: