Question

我有三个活动，MainActivity，OtherActivity，ThirdActivity

MainActivity作为主菜单，将通过按钮指向OtherActivity：

public void onClick(View v) {
        Intent myIntent = new Intent(MainActivity.this, OtherActivity.class);
        MainActivity.this.startActivity(myIntent);
    }

然后在OtherActivity中包含需要输入下一个活动的数据表格列表，即ThirdActivity

public class OtherActivity extends Activity {

EditText Name, Age, MPersonal, MBTI, Birthday, SNotes;
Button second button, third button;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.other_activity);
    Intent myIntent = getIntent();
    secondbutton = (Button)findViewById(R.id.secondbutton);
    thirdbutton = (Button)findViewById(R.id.button3);
    Name = (EditText) findViewById(R.id.editText);
    Age = (EditText) findViewById(R.id.editText2);
    MPersonal = (EditText) findViewById(R.id.editText3);
    MBTI = (EditText) findViewById(R.id.editText4);
    Birthday = (EditText) findViewById(R.id.editText5);
    SNotes = (EditText) findViewById(R.id.editText6);

}
public void onClick2(View view) {
    Intent backIntent = new Intent(OtherActivity.this, MainActivity.class);
    OtherActivity.this.startActivity(backIntent);
}
public void onClick3(View view) {
    Intent bintent = new Intent(this, ThirdActivity.class);
    Bundle bbundle = new Bundle();
    bbundle.putString("name", Name.getText().toString());
    bbundle.putString("age", Age.getText().toString());
    bbundle.putString("mper", MPersonal.getText().toString());
    bbundle.putString("mbti", MBTI.getText().toString());
    bbundle.putString("birthday", Birthday.getText().toString());
    bbundle.putString("special", SNotes.getText().toString());
    bintent.putExtras(bbundle);
    startActivity(bintent);

}
}

它运行良好，直接向ThirdActivity发送意图，即：

public class ThirdActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.data_activity);
    TextView nameView = (TextView) findViewById(R.id.nametext);
    nameView.setText(getIntent().getExtras().getString("name"));
    TextView ageView = (TextView) findViewById(R.id.agetext);
    ageView.setText(getIntent().getExtras().getString("age"));
    TextView mperView = (TextView) findViewById(R.id.mpersonalitytext);
    mperView.setText(getIntent().getExtras().getString("mper"));
    TextView mbtiView = (TextView) findViewById(R.id.mbtitext);
    mbtiView.setText(getIntent().getExtras().getString("mbti"));
    TextView birthdayView = (TextView) findViewById(R.id.birthdaytext);
    birthdayView.setText(getIntent().getExtras().getString("birthday"));
    TextView specialView = (TextView) findViewById(R.id.specialtext);
    specialView.setText(getIntent().getExtras().getString("special"));
}

Inside ThirdActivity还包含onClick函数并重定向到主菜单：

    public void Clicky (View vclicky) {
    Intent intentclick = new Intent(ThirdActivity.this, MainActivity.class);
    ThirdActivity.this.startActivity(intentclick);
}

效果很好。但是当我尝试返回列出输入数据的ThirdActivity时。我尝试单击按钮时发生错误：

public void onClicky(View vclick) {
    Intent kuriki = new Intent(MainActivity.this, ThirdActivity.class);
    MainActivity.this.startActivity(kuriki);
}

错误消息说：

E / AndroidRuntime：致命异常：主要处理：com.example.user.myapplication，PID：3739 java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.user.myapplication / com.example.user.myapplication.ThirdActivity}：java.lang.NullPointerException：尝试调用虚方法'java.lang.String android。对象引用上的os.BaseBundle.getString（java.lang.String）' 在android.app.ActivityThread.performLaunchActivity（ActivityThread.java:2646）在android.app.ActivityThread.handleLaunchActivity（ActivityThread.java:2707）在android.app.ActivityThread.-wrap12（ActivityThread.java）

底线是当我尝试在OtherActivity中输入数据时，输入的数据以ThirdView中的TextView形式保存。返回按钮将返回主菜单，即MainActivity。然后当我尝试通过单击指向ThirdActivity的Button来查看数据时。发生错误

你能帮我解释为什么我无法返回输入数据，我认为我不理解错误信息。提前致谢

Answer 1

很抱歉迟到了，但我已经搜索并尝试了很多解释给你，并知道错误在哪里，你在帖子中阅读/提供的LogCat最初的错误这些行对你没用或者帮助你了解需要的是这个

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
                                                                                                      at com.blogspot.dictionary.coding.android.tempdeletemenow.ThirdActivity.onCreate(ThirdActivity.java:32)

描述错误，并在代码中表示行号X（对我来说是32）

nameView.setText(getIntent().getExtras().getString("name"));

首先getIntent().getExtras().getString("name")表示您从启动此活动的Intent获取保存的数据（Extras），这是

    public void onClicky(View vclick) {
    Intent kuriki = new Intent(MainActivity.this, ThirdActivity.class);
    MainActivity.this.startActivity(kuriki);
}

（在直接启动ViewData的情况下）没有Extras（保存的数据（名称，年龄......）），所以来自形式的意图首先输入数据然后视图将在查看 no（null）数据崩溃时起作用

解决方法是： -

<强> 1。 IN ThirdActivit：

添加If检查意图的语句是否有数据（附加）
同时检查自己的意图不是= null
用getIntent()意图

bintent

最后在应用上分享bintent意图，以便在static

喜欢这个

import static com.blogspot.dictionary.coding.android.tempdeletemenow.MainActivity.bintent;


public class ThirdActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.data_activity);

    if (bintent != null) {
        if (bintent.hasExtra("name")) {
            TextView nameView = (TextView) findViewById(R.id.nametext);
            TextView ageView = (TextView) findViewById(R.id.agetext);
            TextView mperView = (TextView) findViewById(R.id.mpersonalitytext);
            TextView mbtiView = (TextView) findViewById(R.id.mbtitext);
            TextView birthdayView = (TextView) findViewById(R.id.birthdaytext);
            TextView specialView = (TextView) findViewById(R.id.specialtext);

            nameView.setText(bintent.getExtras().getString("name"));
            ageView.setText(bintent.getExtras().getString("age"));
            mperView.setText(bintent.getExtras().getString("mper"));
            mbtiView.setText(bintent.getExtras().getString("mbti"));
            birthdayView.setText(bintent.getExtras().getString("birthday"));
            specialView.setText(bintent.getExtras().getString("special"));
        }
    }
}

<强> 2。 IN MainActivity

public class MainActivity extends Activity {

static Intent bintent;

@Override
protected void onCreate(Bundle savedInstanceState) {

第3。最后，IN OtherActivity

import static com.blogspot.dictionary.coding.android.tempdeletemenow.MainActivity.bintent;

并在Intent

之前移除bintent = new Intent(this, ThirdActivity.class);

输入数据后返回数据列表

1 个答案: