我的Android应用在启动时崩溃

Question

我正在尝试构建一个显示新故事的基本应用程序（当前已硬编码到Strings.xml文件中）。 但是，即使代码中没有显示任何错误，它也会在启动时崩溃。

这是我代码的Java部分（我也可以提供其他文件，甚至可以提供我工作区的压缩副本，如果有帮助的话）

package cara.app;

import android.os.Build;  
import android.os.Bundle;  
import android.annotation.SuppressLint;  
import android.app.Activity;  
import android.content.res.Resources;  
import android.view.Menu;  
import android.view.View;  
import android.widget.Button;  
import android.widget.TextView;  


public class MainActivity extends Activity {

    final Resources res = getResources();
    final TextView textView = new TextView(null);
    final Button next = (Button) findViewById(R.id.LinearLayout1);

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

        final Button button = (Button) findViewById(R.id.LinearLayout1);
        button.setText("" + res.getString(R.string.News) + "\n\n" + res.getString(R.string.Story_Title_1) + "\n\n" + res.getString(R.string.Story_Title_2) + "\n\n" + res.getString(R.string.Story_Title_3) + "\n\n" + res.getString(R.string.Story_Title_4) + "\n\n" + res.getString(R.string.Story_Title_5));

        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {                   
                OpenNews();
            }
        });

        // 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);
        }

}
public void selfDestruct(View view) {
    // Boom 
}


@SuppressLint("NewApi")
@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;
}

public void OpenNews()
{

    // Create the text view
    textView.setTextSize(40);
    textView.setText(res.getString(R.string.Story_1));

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

    next.setText("Next");

    next.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        int itemNumber = 1;

        if(itemNumber == 1){
            textView.setText(res.getString(R.string.Story_2));
            itemNumber = 2;
        }
        else if(itemNumber == 2){
            textView.setText(res.getString(R.string.Story_3));
            itemNumber = 3;
        }
        else if(itemNumber == 3){
            textView.setText(res.getString(R.string.Story_4));
            itemNumber = 4;
        }
        else if(itemNumber == 4){
            textView.setText(res.getString(R.string.Story_5));
            itemNumber = 5;
        }
        else if(itemNumber == 5){
            textView.setText(res.getString(R.string.Story_1));
            itemNumber = 1;
        }
    }


});
}

}

Answer 1

我认为是因为

final Button button = (Button) findViewById(R.id.LinearLayout1);

检查您的activity_main.xml并传递button的ID而不是LinearLayout1 。

也将此代码移到onCreate内的以下代码中

final Button next = (Button) findViewById(R.id.LinearLayout1);
final Resources res = getResources();
final TextView textView = new TextView(null);

Answer 2

将这些内容移到setContentView之后的onCreate中

 Resources res;
 TextView textView;
 Button next; 
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 res = getResources(); 
 textView = new TextView(this); // use Activity COntext
 next = (Button) findViewById(R.id.LinearLayout1);

getResources()是Context的方法，并且Activity创建后即可使用Activity Context。 findViewById在当前infalted布局中查找具有ID的视图。 您需要将布局设置为活动，然后初始化视图。

最后

public TextView (Context context)

但是你有

TextView textView = new TextView(null);

代替null使用this 。

你也有

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

对同一Activity的setContentView两次以上是一个糟糕的设计。

同样使用此textView = new TextView(this); 您有一个textview，但是没有添加到活动中。

阅读

http://developer.android.com/training/basics/firstapp/starting-activity.html

Answer 3

尝试以这种方式进行。

    private Button next = null;

    @SuppressLint("NewApi")
@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        next  = (Button) findViewById(R.id.LinearLayout1);
        final Button button = (Button) findViewById(R.id.LinearLayout1);
        button.setText("" + res.getString(R.string.News) + "\n\n" + res.getString(R.string.Story_Title_1) + "\n\n" + res.getString(R.string.Story_Title_2) + "\n\n" + res.getString(R.string.Story_Title_3) + "\n\n" + res.getString(R.string.Story_Title_4) + "\n\n" + res.getString(R.string.Story_Title_5));

        button.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {                   
                OpenNews();
            }
        });