Question

我是Android编程的新手，我尝试按照提供的方式执行活动2 https://developer.android.com/training/basics/firstapp/starting-activity.html 预期的输出是，在单击发送按钮后，应显示在文本框中键入的任何内容。但是，唯一可见的输出是HelloWorld。你能否告诉我需要做出哪些改变才能获得预期的产量。

我已按照教程中提供的确切步骤进行操作。

其他细节： Windows操作系统 - 8 Java 7

提前致谢!!

package com.example.myfirstapp;
import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class DisplayMessageActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // 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 as the activity layout
        setContentView(textView);
        setContentView(R.layout.activity_display_message);

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }



    @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();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_display_message,
                    container, false);
            return rootView;
        }
    }

}

XML

<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="com.example.myfirstapp.DisplayMessageActivity$PlaceholderFragment" >

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/hello_world" />

Answer 1

错误在于：

setContentView(textView);
setContentView(R.layout.activity_display_message);

==＆GT;你调用setContentView 两次，最后一个调用是将要使用的那个。根据{{3}}你应该有：

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

Answer 2

您很可能错过了处理点击事件的一些步骤。别忘了在Button元素中添加onClick。

还在MainActivity中添加此方法：

/** 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);
}

Android活动2相关（在Android培训的开发人员部分中提供）

2 个答案: