dataView中的错误

Question

我正在从一本书中学习为android开发应用程序，在遵循了说明之后，我最终得到了以下内容。

private void setStartUpScreenText(){
    TextView planetNameValue =  (TextView)findViewById(R.id.dataView1);
    planetNameValue.setText(earth.planetName);

我在findViewById()中的dataView1下面看到了红色的波浪形下划线。Eclipse通知dataView1无法解析或不是字段。

完整的代码如下所示，我在所有的dataView下面都有一个红色的波浪形下划线。书中没有提到这个错误。

private void setStartUpScreenText(){
    TextView planetNameValue =  (TextView)findViewById(R.id.dataView1);
    planetNameValue.setText(earth.planetName);
    TextView planetMassValue = (TextView)findViewById(R.id.dataView2);
    planetMassValue.setText(String.valueOf(earth.planetMass));
    TextView planetGravityValue = (TextView)findViewById(R.id.dataView3);
    planetGravityValue.setText(String.valueOf(earth.planetGravity));
    TextView planetColoniesValue = (TextView)findViewById(R.id.dataView4);
    planetColoniesValue.setText(String.valueOf(earth.planetColonies));
    TextView planetPopulationValue = (TextView)findViewById(R.id.dataView5);
    planetPopulationValue.setText(String.valueOf(earth.planetPopulation));
    TextView planetMilitaryValue = (TextView)findViewById(R.id.dataView6);
    planetMilitaryValue.setText(String.valueOf(earth.planetMilitary));
    TextView planetBasesValue = (TextView)findViewById(R.id.dataView7);
    planetBasesValue.setText(String.valueOf(earth.planetBases));
    TextView planetForceFieldValue = (TextView)findViewById(R.id.dataView8);
    planetForceFieldValue.setText(String.valueOf(earth.planetProtection));

这里是MainActivity

public class MainActivity extends ActionBarActivity {
WorldGen earth = new WorldGen("Earth", 5973, 9.78);

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

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

protected void setStartUpWorldValue(){
    earth.setPlanetColonies(1);
    earth.setPlanetMilitary(1);
    earth.setColonyImmigration(1000);
    earth.setBaseProtection(100);
    earth.turnForceFieldOn();

}

private void setStartUpScreenText(){
    TextView planetNameValue =  (TextView)findViewById(R.id.dataView1);
    planetNameValue.setText(earth.planetName);
    TextView planetMassValue = (TextView)findViewById(R.id.dataView2);
    planetMassValue.setText(String.valueOf(earth.planetMass));
    TextView planetGravityValue = (TextView)findViewById(R.id.dataView3);
    planetGravityValue.setText(String.valueOf(earth.planetGravity));
    TextView planetColoniesValue = (TextView)findViewById(R.id.dataView4);
    planetColoniesValue.setText(String.valueOf(earth.planetColonies));
    TextView planetPopulationValue = (TextView)findViewById(R.id.dataView5);
    planetPopulationValue.setText(String.valueOf(earth.planetPopulation));
    TextView planetMilitaryValue = (TextView)findViewById(R.id.dataView6);
    planetMilitaryValue.setText(String.valueOf(earth.planetMilitary));
    TextView planetBasesValue = (TextView)findViewById(R.id.dataView7);
    planetBasesValue.setText(String.valueOf(earth.planetBases));
    TextView planetForceFieldValue = (TextView)findViewById(R.id.dataView8);
    planetForceFieldValue.setText(String.valueOf(earth.planetProtection));


}

Answer 1

您似乎是在fragment_main.xml而不是activity_main.xml.中构建视图的

当您第一次创建新的android项目时，会自动创建和打开以下文件：

​

​

然后，在开始时，在fragment_main.xml文件中添加视图(例如: TextView)。最后，您尝试在Activity中使用此视图执行一个基本事件，如下所示：

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main); // Using layout activity_main.xml

        // You try to set a simple text on the view (TextView) previously added
        TextView text = (TextView) findViewById(R.id.textView1);
        text.setText("Simple Text");  // And you get an error here!

        /*
         * You do an fragment transaction to add PlaceholderFragment Fragment
         * on screen - this below snippnet is automatically created.
        */
        if(savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    } 

您不能运行您的应用程序，或者有时您只有一个白屏，因为您试图调用/显示的视图布局错误。

解决方案：将onCreateView方法中的所有内容移到片段类中。

调用视图并在相关片段中执行某些操作，而不是在父活动中。

或者，您可以在活动中执行所有操作，方法是删除不在UI上添加片段的这些行：

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

这将在您的活动布局“上方”创建并添加一个片段。然后，在这里设置正确的布局：

setContentView(R.layout.fragment_main);