1

下一个问题..哈哈（我有很多）。

我想将我的 textViews 更改为 Bundle.getExtras(); 的内容；

我在stackoverflow上找到了这个例子

final TextView textViewToChange = (TextView) findViewById(R.id.completeCurrentMod);
    textViewToChange.setText(
        "The new text that I'd like to display now that the user has pushed a button.");

但是，当我将它放入我的应用程序时，它会引发错误。

07-26 20:38:50.993: E/AndroidRuntime(31862): 致命异常: main 07-26 20:38:50.993: E/AndroidRuntime(31862): java.lang.RuntimeException: 无法启动活动 ComponentInfo{com. example.smallchangebigloss/com.example.smallchangebigloss.Complete}：java.lang.NullPointerException 07-26 20:38:50.993：E/AndroidRuntime(31862)：在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2460) 07 -26 20:38:50.993: E/AndroidRuntime(31862): 在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2521) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在 android.app .ActivityThread.access$600(ActivityThread.java:162) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1370) 07-26 20: 38：50.993：E/AndroidRuntime（31862）：在 android.os.Handler。dispatchMessage(Handler.java:99) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在 android.os.Looper.loop(Looper.java:158) 07-26 20:38:50.993: E/ AndroidRuntime(31862): 在 android.app.ActivityThread.main(ActivityThread.java:5777) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在 java.lang.reflect.Method.invokeNative(Native Method) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在 java.lang.reflect.Method.invoke(Method.java:511) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1083) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在 com.android.internal.os.ZygoteInit.main(ZygoteInit .java:850) 07-26 20:38:50.993: E/AndroidRuntime(31862): at dalvik.system.NativeStart.main(Native Method) 07-26 20:38:50.993: E/AndroidRuntime(31862): Caused经过：java.lang.NullPointerException 07-26 20:38:50.993: E/AndroidRuntime(31862): at com.example.smallchangebigloss.Complete.onCreate(Complete.java:17) 07-26 20:38:50.993: E/AndroidRuntime (31862): 在 android.app.Activity.performCreate(Activity.java:5165) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1103) 07-26 20:38:50.993: E/AndroidRuntime(31862): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) 07-26 20:38:50.993: E/AndroidRuntime(31862): ... 11 更多 07-26 20:39:40.676: E/AndroidRuntime(32566): FATAL EXCEPTION: main 07-26 20:39:40.676: E/AndroidRuntime(32566): java.lang.RuntimeException: Unable to start activity ComponentInfo{ com.example.smallchangebigloss/com.example.smallchangebigloss.Complete}：java.lang。NullPointerException 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2460) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 android .app.ActivityThread.handleLaunchActivity(ActivityThread.java:2521) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 android.app.ActivityThread.access$600(ActivityThread.java:162) 07-26 20: 39:40.676: E/AndroidRuntime(32566): 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1370) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 android.os.Handler .dispatchMessage(Handler.java:99) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 android.os.Looper.loop(Looper.java:158) 07-26 20:39:40.676: E /AndroidRuntime(32566): 在 android.app.ActivityThread.main(ActivityThread.java:5777) 07-26 20:39:40.676:E/AndroidRuntime(32566): at java.lang.reflect.Method.invokeNative(Native Method) 07-26 20:39:40.676: E/AndroidRuntime(32566): at java.lang.reflect.Method.invoke(Method. java:511) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1083) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:850) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 dalvik.system.NativeStart.main （本机方法）07-26 20:39:40.676：E/AndroidRuntime（32566）：由：java.lang.NullPointerException 07-26 20:39:40.676：E/AndroidRuntime（32566）：在 com.example.smallchangebigloss .Complete.onCreate(Complete.java:17) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 android.app.Activity.performCreate(Activity.java:5165) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1103) 07-26 20:39:40.676: E/AndroidRuntime(32566): 在android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) 07-26 20:39:40.676: E/AndroidRuntime(32566): ... 11 更多 07-26 20:40:38.598: E/AndroidRuntime(586) ：致命异常：主要 07-26 20:40:38.598：E/AndroidRuntime(586)：java.lang.RuntimeException：无法启动活动 ComponentInfo{com.example.smallchangebigloss/com.example.smallchangebigloss.Complete}：java。 lang.NullPointerException 07-26 20:40:38.598: E/AndroidRuntime(586): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2460) 07-26 20:40:38.598: E/AndroidRuntime(586):在 android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2521) 07-26 20:40:38.598: E/AndroidRuntime(586): 在 android.app.ActivityThread.access$600(ActivityThread.java:162) 07-26 20:40:38.598: E/AndroidRuntime(586 ): 在 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1370) 07-26 20:40:38.598: E/AndroidRuntime(586): 在 android.os.Handler.dispatchMessage(Handler.java:99) 07-26 20:40:38.598: E/AndroidRuntime(586): 在 android.os.Looper.loop(Looper.java:158) 07-26 20:40:38.598: E/AndroidRuntime(586): 在 android. app.ActivityThread.main(ActivityThread.java:5777) 07-26 20:40:38.598: E/AndroidRuntime(586): 在 java.lang.reflect.Method.invokeNative(Native Method) 07-26 20:40:38.598 : E/AndroidRuntime(586): at java.lang.reflect.Method.invoke(Method.java:511) 07-26 20:40:38.598: E/AndroidRuntime(586): at com.android.internal.os。ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1083) 07-26 20:40:38.598: E/AndroidRuntime(586): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:850) 07-26 20：40：38.598：E/AndroidRuntime（586）：在 dalvik.system.NativeStart.main（本机方法）07-26 20：40：38.598：E/AndroidRuntime（586）：引起：java.lang.NullPointerException 07 -26 20:40:38.598: E/AndroidRuntime(586): 在 com.example.smallchangebigloss.Complete.onCreate(Complete.java:20) 07-26 20:40:38.598: E/AndroidRuntime(586): 在 android .app.Activity.performCreate(Activity.java:5165) 07-26 20:40:38.598: E/AndroidRuntime(586): 在 android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1103) 07-26 20:40 :38.598: E/AndroidRuntime(586): 在 android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) 07-26 20:40:38.598:E/AndroidRuntime(586): ... 11 更多

当我单击下一步时，这门课失败了。

package com.example.smallchangebigloss;

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

public class GoalWeight extends Activity {

    private EditText edit;
    private String name,current;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_goal_weight);
        Bundle extras = getIntent().getExtras();
        name = extras.getString("name");
        current = extras.getString("current");




        edit = (EditText) findViewById(R.id.currentWeightEdit);
    }

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

    public void next(View view) {
        if (edit.getText().toString().equals("")) {
            new AlertDialog.Builder(this).setTitle("Ut Oh!")
                    .setMessage("Please enter your Goal Weight.")
                    .setNeutralButton("Try again", null).show();
        }
        else {
            Intent i = new Intent(getApplicationContext(), Complete.class);
            i.putExtra("goal", edit.getText().toString());
            i.putExtra("current", current);
            i.putExtra("name", name);


            startActivity(i);

        }
    }

}

这是下一节课：

package com.example.smallchangebigloss;

import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.widget.TextView;

public class Complete extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle extras = getIntent().getExtras();
        final TextView textViewToChange = (TextView) findViewById(R.id.completeCurrentMod);
        textViewToChange.setText(
            "The new text that I'd like to display now that the user has pushed a button.");
        System.out.println("name: " + extras.getString("name") + "Current weight: "
                + extras.getString("current") + "goal: " + extras.getString("goal"));

    }

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

}

提前致谢。

4

1 回答 1

4

你还没有打电话setContentView()所以你TextView是null

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Bundle extras = getIntent().getExtras();

   // You need to call setContentView(R.layout.your_layout_file)
    final TextView textViewToChange = (TextView) findViewById(R.id.completeCurrentMod);
    textViewToChange.setText(
        "The new text that I'd like to display now that the user has pushed a button.");

如果您尝试View在充气之前初始化您的，layout它包含在使用 aLayoutInflater或通过调用setContentView()您的Viewwillnull因此，NPE当您尝试在其上调用方法时，例如setText()

于 2013-07-26T19:50:53.183 回答